Make sure that we always pop a function's scope *before* we call

Make sure that we always pop a function's scope *before* we call
ActOnFinishFunctionBody/ActOnBlockStmtExpr. This way, we ensure that
we diagnose undefined labels before the jump-scope checker gets run,
since the jump-scope checker requires (as its invariant) that all of
the GotoStmts be wired up correctly.

Fixes PR9495.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@127738 91177308-0d34-0410-b5e6-96231b3b80d8