Revert "Features: Record for AppleClang."

This reverts commit 4916cff87df8e8bc2e4100f6850886f367ba3c1e.
Merge topic 'AppleClang-features' into next

3c545978 Revert "Features: Record for AppleClang."
Features: Don't record for AppleClang

Features are currently recorded accidentally for all versions of
AppleClang > 3.4 (I have no idea how that relates to upstream
Clang). Presumably that version has the features which are
accidentally recorded, but in the future features will be
recorded initially for only AppleClang >= 5.1, which would
appear as a feature regression.

Commit v3.1.0-rc1~635^2~11 (Don't load Clang-CXX from
AppleClang-CXX., 2013-11-11) ajusted the logic for the CXX
language.  Make a similar change for the C language.
Merge topic 'no-AppleClang-C-features' into next

ded30405 Features: Don't record for AppleClang