[analyzer] isCLibraryFunction: check that the function is at TU-scope.

Also, Decls already carry a pointer to the ASTContext, so there's no need
to pass an extra argument to the predicate.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@167337 91177308-0d34-0410-b5e6-96231b3b80d8
3 files changed