Add System_Parse_CommandForUnix to the KWSys System interface as a
utility to parse a unix-style command line.  Move the existing
implementation out of ProcessUNIX.  Add a flags argument reserved for
future use in providing additional behavior.

This adds another cast to avoid pointer conversion warnings.
Unfortunately C does not recognize implicit conversions that add
cv-qualifiers as well as C++ does.

COMP: Eliminate "conversion may change sign of result" warnings by using size_t where appropriate. (Missed one warning with last commit: add a cast to md5_word_t.)

This uses size_t where necessary to avoid size_t/int conversion
warnings.

This adds const-ness and casts where necessary to avoid pointer
conversion warnings.

This disables Borland warning 8027 while compiling KWSys source files.
It provides no useful information.

This removes an assignment whose result is never used, thus quieting a
warning from Borland.

This helps avoid fixing VMS-specific code for non-VMS compilers where it
isn't needed anyway.

COMP:Fixed warning with gcc 4.3.3: passing argument 1 of kwsysProcessSetVMSFeature discards qualifiers from pointer target type.

The KWSys String implementation of strcasecmp initialized 'result'
immediately before assigning to it.  Borland produces a warning in this
case, so this commit removes the extra initialization.

This teaches ConvertToUnixSlashes to convert VMS paths into posix-style
paths.  We also set the DECC$FILENAME_UNIX_ONLY feature so the process
always sees posix-style paths on disk.

This achieves basic process execution on OpenVMS.  We use work-arounds
for different fork()/exec() behavior and a lack of select().

VMS emulates fork/exec using setjmp/longjmp to evaluate the child and
parent return cases from fork.  Therefore both must be invoked from the
same function.

Since select() works only for sockets we use the BeOS-style polling
implementation.  However, non-blocking reads on empty pipes cannot be
distinguished easily from the last read on a closed pipe.  Therefore we
identify end of data by an empty read after the child terminates.

This avoids use of an uninitialized value in the KWSys ProcessUNIX
polling implementation when no timeout is given.

The Compaq compiler (on VMS) includes 'String.c' in source files that
use the stl string while looking for template definitions.  This was the
true cause of double-inclusion of the 'kwsysPrivate.h' header.  We work
around the problem by conditionally compiling the entire source file on
a condition only true when really building the source.

The kwsysPrivate header double-inclusion check hits a false positive on
VMS for an undetermined reason.  This simplifies the workaround and
documents it.

Read-only directories must be given write permission before we can
remove files and subdirectories from them.

ENH: check in almost building VMS stuff with VMSBuild directory since the bootstrap script will not work on VMS

Alex

This removes SystemTools::FileExistsInParentDirectories from KWSys since
it is a special-purpose method that is not generally useful.

When SystemTools::GetParentDirectory was fixed to never remove the root
path component from a full path we violated an assumption made by
IsSubDirectory that eventually GetParentDirectory returns an empty
string.  This led to an infinite loop if the potential parent directory
is empty, so we explicitly avoid that case.

The previous change to this method broke cases where the input path does
not exist.  The SystemTools::GetParentDirectory method is redundant with
the more robust SystemTools::GetFilenamePath.  This replaces its
implementation to just call GetFilenamePath.

BUG: SystemTools::GetParentDirectory() will crash if "/" is passed in as argement. Valid check is added to make sure the input argment exists, and if "/" is passed in, empty string will be returned.

All KWSys C symbol names begin with the KWSYS_NAMESPACE defined at
configuration time.  For ease of editing we write canonical names with
the prefix 'kwsys' and use macros to map them to the configured prefix
at preprocessing time.  In the case of standalone KWSys, the prefix is
'kwsys', so the macros were previously defined to their own names.

We now skip defining the macros in the identity case so that the final
symbol names are never themselves macros.  This will allow the symbols
to be further transformed behind the scenes to help linkers in special
cases on some platforms.

Previously KWSys SystemInformation parsed this file assuming a strict
order and set of fields, but the order is not reliable.  This
generalizes the implementation to support any order and extra fields.

BUG: comment out faulty seekp which make kwsys::*stringstream fails on platform with no std::*stringstream implementation