VS: Remove support for "free" version 2003 tools

Several more recent Visual Studio Express editions are now available and
they support debug builds.  Simplify our VS platform files by removing
support for these old tools.  If anyone still uses them we can restore
support with a more modern way to test for them.
Make platform information files specific to the CMake version

At the top of a build tree we configure inside the CMakeFiles directory
files such as "CMakeSystem.cmake" and "CMake<lang>Compiler.cmake" to
save information detected about the system and compilers in use.  The
method of detection and the exact results store varies across CMake
versions as things improve.  This leads to problems when loading files
configured by a different version of CMake.  Previously we ignored such
existing files only if the major.minor part of the CMake version
component changed, and depended on the CMakeCache.txt to tell us the
last version of CMake that wrote the files.  This led to problems if the
user deletes the CMakeCache.txt or we add required information to the
files in a patch-level release of CMake (still a "feature point" release
by modern CMake versioning convention).

Ensure that we always have version-consistent platform information files
by storing them in a subdirectory named with the CMake version.  Every
version of CMake will do its own system and compiler identification
checks even when a build tree has already been configured by another
version of CMake.  Stored results will not clobber those from other
versions of CMake which may be run again on the same tree in the future.
Loaded results will match what the system and language modules expect.

Rename the undocumented variable CMAKE_PLATFORM_ROOT_BIN to
CMAKE_PLATFORM_INFO_DIR to clarify its purpose.  The new variable points
at the version-specific directory while the old variable did not.
Move CMAKE_<LANG>_COMPILER_WORKS to compiler information files

Since the parent commit this test result is specific to the version of
CMake.  Store it in the version-specific compiler information files
instead of CMakeCache.txt so testing can be re-done to meet the
requirements of the current version of CMake even if another version of
CMake was already used to configure the build tree.
Store ABI detection results in compiler information files

Drop use of cache entry CMAKE_DETERMINE_<LANG>_ABI_COMPILED and replace
it with variable CMAKE_<LANG>_ABI_COMPILED.  Since the grandparent
commit this test result is specific to the version of CMake.  Store it
in the version-specific compiler information files instead of
CMakeCache.txt so testing can be re-done to meet the requirements of the
current version of CMake even if another version of CMake was already
used to configure the build tree.
VS: Simplify MSVC version reporting

Teach Windows-cl.cmake to use CMAKE_(C|CXX)_COMPILER_VERSION to set the
"MSVC##" and MSVC_VERSION variables.  It no longer needs the IDE generator
to dictate the version or to detect the version by running the
command-line tool for NMake and Ninja generators.  Drop configuration of
CMakeCPlatform.cmake and CMakeCXXPlatform.cmake from Windows-cl.cmake.in
because all the results it saved are now cheap to compute every time.
Modernize MSVC compiler information files

Remove the old-style "Windows-cl.cmake" and its helper "cl.cmake".  Load
the information through new-style "Platform/Windows-MSVC-<lang>.cmake"
files.  Factor information common to C and CXX into a helper file
"Platform/Windows-MSVC.cmake" loaded from the per-language files.
Merge branch 'cmake-platform-info-version' into msvc-compiler-info

Conflicts:
	Modules/CMakeTestCCompiler.cmake
	Modules/CMakeTestCXXCompiler.cmake
	Modules/Platform/Windows-cl.cmake
Merge topic 'cmake-platform-info-version'

e5fee8a Store ABI detection results in compiler information files
3df81b4 Move CMAKE_<LANG>_COMPILER_WORKS to compiler information files
7195aca Make platform information files specific to the CMake version
Merge topic 'msvc-compiler-info'

32b7c72 Merge branch 'cmake-platform-info-version' into msvc-compiler-info
f3ddfef Modernize MSVC compiler information files
485a940 VS: Simplify MSVC version reporting
32db033 VS: Remove support for "free" version 2003 tools