CMakeDetermineVSServicePack: Improve documentation

Refer users to the newer CMAKE_<LANG>_COMPILER_VERSION variables.
Use a more concise summary.  Format the documentation to look
better in the "cmake --help-module" output.
CMakeDetermineVSServicePack: Add VS 11 update 1 and 2 (#14239)
Merge topic 'CMakeDetermineVSServicePack-vs11' into next

2aa62e0 CMakeDetermineVSServicePack: Add VS 11 update 1 and 2 (#14239)
1746a35 CMakeDetermineVSServicePack: Improve documentation