Preserve Sema::UndefinedInternals across PCH boundaries. Fixes
-Wundefined-internal warnings with PCH.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@173538 91177308-0d34-0410-b5e6-96231b3b80d8
Comment parsing: actually check for a block command after "\param x"

This fixes PR15068.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@173539 91177308-0d34-0410-b5e6-96231b3b80d8
Revert r172285 (suppressing a 'redundant' -Wc++98-compat warning) and add a
testcase for a situation it caused us to miss.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@173540 91177308-0d34-0410-b5e6-96231b3b80d8
Since we're stuck with realpath for the header <-> module mapping,
factor the realpath calls into FileManager::getCanonicalName() so we
can cache the results of this epically slow operation. 5% speedup on
my modules test, and realpath drops out of the profile.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@173542 91177308-0d34-0410-b5e6-96231b3b80d8