[libclang] Fix operations (token annotation, getting cursor, etc.) with a file region

[libclang] Fix operations (token annotation, getting cursor, etc.) with a file region
inside an objc container that "contains" other file-level declarations.

When getting the array of file-level declarations that overlap with a file region,
we failed to report that the region overlaps with an objc container, if
the container had other file-level declarations declared lexically inside it.

Fix this by marking such declarations as "isTopLevelDeclInObjCContainer" in the AST
and handling them appropriately.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@145109 91177308-0d34-0410-b5e6-96231b3b80d8