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.
Move the Version member to the top cmLocalVisualStudioGenerator class
and set it consistently for instances created by all the global
generator versions. Use an enumeration type with values scaled by a
factor of 10 so we can handle VS 7.1 without out-of-order numbers.
VS 7.1 support for SuppressStartupBanner was broken by commit 25116a3c
(Fix CMAKE_VERBOSE_MAKEFILE for VS10 vcxproj files, 2011-10-11) because
it assumed comparison of VS version numbers works. Now it does.
This converts the CMake 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 CMake copyright to
cover the full development time range.