clang_getCXTUResourceUsage: report memory used by HeaderSearch.

This required converting the StringMaps to use a BumpPtrAllocator.  I measured the
compile time and saw no observable regression.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@136190 91177308-0d34-0410-b5e6-96231b3b80d8
4 files changed