When we're inserting a synthesized label declaration for a

forward-looking "goto" statement, make sure to insert it *after* the
last declaration in the identifier resolver's declaration chain that
is either outside of the function/block/method's scope or that is
declared in that function/block/method's specific scope. Previously,
we could end up inserting the label ahead of declarations in inner
scopes, confusing C++ name lookup.

Fixes PR9491/<rdar://problem/9140426> and <rdar://problem/9135994>.

Note that the crash-on-invalid PR9495 is *not* fixed. That's a
separate issue.

llvm-svn: 127737