Replace old hacks of the form 'if("${VAR}" MATCHES "^${VAR}$")'
with the much simpler 'if(NOT DEFINED ${VAR})'.

Change-Id: Ie0e2fc5ceb85156221abe8938dfdd148b3862742

Add supprt for C++ name demangling during call stack
introspection. This will be enabled at compile time
if the required system libraries,header files, and
compiler features are detected. Add a method so that
the stack trace may be obtained on demand not just
from within the stack trace signal handler.

Change-Id: Ie829f4b24ab331e39b97f54e63564df70f129b7e

In commit 'Create KWSYS_PLATFORM_INFO_TEST macro' (2009-11-20) we
implemented the macro to use a cache entry to avoid re-running the
try_compile().  However, the output copied from the try_compile is
needed on every configure.  If the user wipes out the build tree but not
the cache file then the try_compile() will not re-run to recreate the
needed file.  We address the problem by teaching the macro to run the
try_compile() whenever its output file does not exist.

This macro helps KWSys perform try-compile tests that extract 'INFO'
strings out of compiled binaries.  It works for CMake 2.6 and above.
On CMake 2.4 it always returns an empty list of information values,
so this should be used only as an optimization until 2.6 is required.

This converts the KWSys license to a pure 3-clause OSI-approved BSD
License.  We drop the previous license clause requiring modified
versions to be plainly marked.  We also update the KWSys copyright to
cover the full development time range.

ENH: Renamed kwsysPlatformCxxTests to kwsysPlatformTests and generalized it for multiple language tests (C and CXX).

BUG: When a try-run fails to compile create the run result cache entry with a bogus non-zero return value to avoid running the test again.

ENH: Added istream and ostream operators for stl string in KWSys when using old streams that do not provide them.

ENH: Added istream and ostream operators for stl string when using old streams that do not provide them.

ERR: Removed use of FILE command and using WRITE_FILE instead.  We would still like CMake 1.6 to be able to build CMake CVS, and kwsys is used.

ENH: Split kwsys_std into kwsys_ios and kwsys_stl in order to avoid std namespace pollution and support more platforms.