CMake Nightly Date Stamp
tests: Remove variable_expansion test reference
Merge topic 'variable-expansion-tests' into next

41ef3af6 tests: Remove variable_expansion test reference
Help: Document the purpose of usage requirements clearly.

People will be tempted to put things there for convenience, thereby
causing conflicts similar to

 http://thread.gmane.org/gmane.comp.compilers.clang.devel/35162/focus=35169

where it is conceivable that the LLVM developers could put a flag on
a target for convenience, which would cause conflicts for some downstreams.
Merge topic 'doc-usage-requirements' into next

0c54b775 Help: Document the purpose of usage requirements clearly.
586d2ce8 CMake Nightly Date Stamp