[AST/libclang] Speed up clang_getOverriddenCursors() considerably by reserving a bit
in ObjCMethodDecl to indicate whether the method does not override any other method,
which is the majority of cases.

That way we can avoid unnecessary work doing lookups, especially when PCH is involved.

rdar://11360082

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@156476 91177308-0d34-0410-b5e6-96231b3b80d8
8 files changed