c++: fix throwing cleanup with label

c++: fix throwing cleanup with label

While looking at PR92407 I noticed that the expectations of
maybe_splice_retval_cleanup weren't being met; an sk_cleanup level was
confusing its attempt to recognize the outer block of the function.  And
even if I fixed the detection, it failed to actually wrap the body of the
function because the STATEMENT_LIST it got only had the label, not anything
after it.  So I moved the call after poplevel does pop_stmt_list on all the
sk_cleanup levels.

	PR c++/33799

gcc/cp/ChangeLog:

	* except.cc (maybe_splice_retval_cleanup): Change
	recognition of function body and try scopes.
	* semantics.cc (do_poplevel): Call it after poplevel.
	(at_try_scope): New.
	* cp-tree.h (maybe_splice_retval_cleanup): Adjust.

gcc/testsuite/ChangeLog:

	* g++.dg/eh/return1.C: Add label cases.