The AddSource method accepts one file and tries to avoiding adding
it to the sources-list of the target if it already exists.  This
involves creating many cmSourceFileLocation objects for matching
on existing files, which is an expensive operation.

Avoid the searching algorithm by appending the new sources as one
group.  Generate-time processing of source files will ensure
uniqueness.

Add a new AddTracedSources for this purpose.  The existing
AddSources method must process the input for policy CMP0049, but
as these source filenames come from cmSourceFile::GetFullPath(),
we can forego that extra processing.

Computing the language involves computing the source files, which
is an expensive operation.  It requires calling
cmMakefile::GetOrCreateSource many times, which involves creating
and matching on many cmSourceFileLocation objects.

Source files of a target may depend on the head-target and the
config as of commit e6971df6 (cmTarget: Make the source files depend
on the config., 2014-02-13).  The results are cached for each context
as of commit c5b26f3b (cmTarget: Cache the cmSourceFiles in
GetSourceFiles., 2014-04-05).

Each target in the build graph causes language computation of all
of its dependents with itself as the head-target.  This means that
for 'core' libraries on which everything depends, the source files
are computed once for every transitive target-level-dependee and
the result is not cached because the head-target is different. This
was observed in the VTK buildsystem.

Short circuit the computation for targets which have a source-list
that is independent of the head-target.  If the source-list has
already been computed and the generator expression evaluation
reports that it was context-independent, return the only source-list
already cached for the target.  Reset the short-circuit logic when
sources are added and when the link libraries are re-computed.

a4e6bf8e cmTarget: Make GetSourceFiles string overload private.
92e2fbe1 cmGeneratorTarget: Trace cmSourceFile objects instead of strings.
c5b26f3b cmTarget: Cache the cmSourceFiles in GetSourceFiles.
eb163f37 cmTarget: Extract a ProcessSourceItemCMP0049 method.
19b7c22d Ninja: Query custom commands once per target, not once per file.

Consumers should use the cmSourceFile overload, which is now
always the case.

This reverses the decision in commit d38423ec (cmTarget: Add a
method to obtain list of filenames for sources., 2014-03-17).  The
cmSourceFile based API is preferred because that avoids creation of
many cmSourceFileLocation objects for matching strings, and the
result is cached by cmTarget.

Avoid calling GetSourceFiles with the same result container multiple
times when tracing target dependencies.  The result from the previous
configuration is cached and used later otherwise.

Avoid calling AddSource for each src filename.  That involves
checking each entry for uniqueness and creating a separate
generator expression for each one.

Instead, add a single entry for the list of sources.  The source
files are passed through a uniqueness filter at generate-time, so
duplicates don't matter so much.

Computing the source files is now more expensive, so the Ninja
generator became very slow with a large number of files.

be53734d CompileFlags: Add -AA +hpxstd98 on HP-UX 11.11 with aCC
f4b9c6bb CompileFlags: Test for C++ features after selecting flags

These flags are needed to enable support for C++98.  Also teach the
'bootstrap' script to add them if necessary.

Some flags we select may affect availability of C++ features.

63d864a0 Tests: Fix CTestTestFailedSubmit-ftp with OS X system libcurl

6c190245 Remove extra semicolons from C++ code.
4bef02e7 cmTypeMacro: Add a class to eat the semicolon following the macro use.
ff710539 Remove default labels from fully covered switch statements.

c4059a21 cmTarget: Remove abort() after INTERNAL_ERROR reports

7beba986 Qt4Macros: Make QT4_CREATE_MOC_COMMAND a function

23b4abb2 Merge branch 'upstream-kwsys' into update-kwsys
eccc425a KWSys 2014-04-02 (39f98b5d)

a40f57e4 cmMakefile: Revise comment describing IsOn()

On OS X 10.9 the system libcurl has a different error message when
failing to connect:

  Failed connect to :21; Connection refused

Match this message to pass the test.

f4fe6322 Help: Add notes for topic 'ExternalProject_exclude-from-all'

Clang based tools running over the code complain about these,
but clang has a fixit for removing them.

Apply the same workaround to the cmCPackTypeMacro. Additionally
change that macro to not use 'class' as a macro parameter.

Allow compilers to warn when new enum values are added, making
switches no-longer fully-covered.

After reporting an internal error we should continue rather than
aborting.  Remove such statements that are left from debugging.

QT4_CREATE_MOC_COMMAND is given a moc_flags argument that contains the
COMPILE_DEFINITIONS and a potentially large list of include directories.
Since it is a macro, the ${moc_flags} reference is replaced with this
content and sent through cmMakefile::ExpandVariablesInString (EVIS).
Since commit v3.0.0-rc1~138^2 (Qt4: Use generator expression in
COMPILE_DEFINITIONS, 2014-01-13) the COMPILE_DEFINITIONS value contains
a '$' so the EVIS fast-path is no longer used.  Instead the full
cmCommandArgumentParserHelper is now used on the large input, which is
very slow (since it was originally created for hand-written code).

Change QT4_CREATE_MOC_COMMAND to a function instead of a macro to avoid
passing large content through EVIS.  This makes it significantly faster.

9407174b target_sources: New command to add sources to target.
81ad69e0 Make the SOURCES target property writable.
6e636f2e cmTarget: Make the SOURCES origin tracable.
3676fb49 cmTarget: Allow transitive evaluation of SOURCES property.
e6971df6 cmTarget: Make the source files depend on the config.
df753df9 cmGeneratorTarget: Don't add computed sources to the target.
869328aa cmComputeTargetDepends: Use valid config to compute target depends.

5de63265 Genex: Only evaluate TARGET_OBJECTS to determine target sources.
aa0a3562 cmGeneratorTarget: Compute target objects on demand
042c1c83 cmTarget: Compute languages from object libraries on demand.
fdcefe3c cmGeneratorTarget: Compute consumed object libraries on demand.
c355d108 cmComputeTargetDepends: Track object library depends.
e5da9e51 cmTarget: Allow any generator expression in SOURCES property.
5702e106 cmTarget: Include TARGET_OBJECTS genex in target SOURCES property.
857d30b5 cmGlobalGenerator: Add interface to call ForceLinkerLanguages
28e1d2f8 cmStringCommand: Add GENEX_STRIP subcommand.
bf98cc25 Genex: Evaluate TARGET_OBJECTS as a normal expression.
8cd113ad cmTarget: Store strings instead of cmSourceFile* to represent SOURCES.
4959f341 cmSourceFileLocation: Collapse full path for directory comparisons.
fcc92878 cmSourceFileLocation: Remove unused Update method.
59e8740a cmTarget: Remove AddSourceFile method
26d494ba cmTarget: Use string API to add sources to cmTarget objects.
d38423ec cmTarget: Add a method to obtain list of filenames for sources.
...

13684e2b cmMakefile: Port PolicyOptionalWarningEnabled to string APIs
8018fcca Merge branch 'master' into revise-compiler-id-policies
a41c0a9d Do not warn by default when policy CMP0025 or CMP0047 is not set
d339653e Help: Revise and format policy CMP0025 and CMP0047 docs

391c73db CTestCustom: Suppress conversion warnings in QtWidgets headers

fcdf86d0 Help: Rewrite the cmake-developer.7 find module documentation

1de08685 cmSystemTools: Restore unreachable return to silence warnings

1e22b23c Watcom: Cleanup Windows-wcl386 configuration

936e00b9 Simplify multiple config handling.

e8633e66 VS: Fix /analyze:log flag mapping (#14858)
650199e7 VS: Support mapping flags with values following separately (#14858)
f2a3dd9d cmIDEOptions: Factor FlagMap update out to separate method