Simplify RevertibleTypeTraits as a form of contextual keyword

Now that we emit diagnostics for keyword-as-identifier hacks (-Wkeyword-compat)
we can go ahead and simplify some of the old revertible keyword support.

This commit adds a TryIdentKeywordUpgrade() function to mirror the recently
added TryKeywordIdentFallback() and uses it to replace the hard-coded list of
REVERTIBLE_TYPE_TRAITs.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@197496 91177308-0d34-0410-b5e6-96231b3b80d8
Refactor and micro-optimize ConsumeToken()

1) Introduce TryConsumeToken() to handle the common test-and-consume pattern.
   This brings about readability improvements in the parser and optimizes to avoid
   redundant checks in the common case.

2) Eliminate the ConsumeCodeCompletionTok special case from ConsumeToken(). This
   was used by only one caller which has been switched over to the more
   appropriate ConsumeCodeCompletionToken() function.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@197497 91177308-0d34-0410-b5e6-96231b3b80d8
Remove -f16:16:32 from the XCore DataLayout string.

This makes it identical to the string llvm produces.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@197500 91177308-0d34-0410-b5e6-96231b3b80d8