c++: don't cleanup the last aggregate elt

c++: don't cleanup the last aggregate elt

Now that we're building cleanups for aggregate elements more often, it seems
worth optimizing by avoiding building one for the last element; once it is
initialized, the complete object is fully initialized, the element cleanups
end in favor of the complete object cleanup, and so a cleanup for the last
element would guard nothing at all.

gcc/cp/ChangeLog:

	* typeck2.c (split_nonconstant_init_1): Don't cleanup the last elt.
	(split_nonconstant_init): Adjust.

gcc/testsuite/ChangeLog:

	* g++.dg/tree-ssa/aggregate1.C: New test.