MFC r303841,r312012,r312213:
r303841 (by bdrewery):
Revert r298434 which should be fixed by r301287, r301394, and r301403.
PR: 208703, 208963
r312012:
fmaxmin_test still fails with clang 3.9.x.. bypass the test
PR: 208703
r312213:
Turn COMPILER_VERSION/COMPILER_TYPE make check into a compile-time check
of the clang version
This works around breakage on ^/stable/10 when running installworld from
a ^/stable/10 host where the test wouldn't be compiled on the first
go-around and would be missing when make installworld is run.
PR: 208703