CMake Nightly Date Stamp
Tests: Make CompileFeature tests use highest standard known.

Remove the use of check_cxx_source_compiles which is now just getting in
the way.

Blacklist the cxx_alignof feature in the test with GNU 4.7. The test
file compiles, but it is documented as available first in GNU 4.8.
Merge topic 'minor-cleanups' into next

f5bf9d43 Tests: Make CompileFeature tests use highest standard known.
3547a00d CMake Nightly Date Stamp