Fix the location of "missing ';'" suggestions after annotation tokens.

Fix the location of "missing ';'" suggestions after annotation tokens.

We were incorrectly setting PrevTokLocation to the first token in the
annotation token instead of the last when consuming it. To fix this without
adding a complex switch to the hot path through ConsumeToken, we now have a
ConsumeAnnotationToken function for consuming annotation tokens in addition
to the other Consume*Token special case functions.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@303372 91177308-0d34-0410-b5e6-96231b3b80d8