ENH: UNIX, CYGWIN, WIN32, APPLE, QNXNTO and BEOS are not longer set in
cmMakefile.cxx, but now in the platform files and are now valid for the
target platform, not the host platform.
New variables CMAKE_HOST_WIN32, CMAKE_HOST_UNIX, CMAKE_HOST_APPLE and
CMAKE_HOST_CYGWIN have been added in cmMakefile.cxx (...and have now to be
used in all cmake files which are executed before
CMakeSystemSpecificInformation.cmake is loaded). For compatibility the old
set is set to the new one in CMakeDetermineSystem.cmake and reset before the
system platform files are loaded, so custom language or compiler modules
which use these should still work.

Alex