ASTUnit/CIndex: Explicitly track the top-level decls when using an ASTUnit made
from a source file.
 - This allows CIndex to avoid iterating over all the top-level decls when using
   a PCH, which means we deserialize far fewer decls.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@90559 91177308-0d34-0410-b5e6-96231b3b80d8
4 files changed