c++: assignment, aggregate, array [PR104300]

c++: assignment, aggregate, array [PR104300]

The PR92385 fix meant that we see more VEC_INIT_EXPR outside of INIT_EXPR;
in such cases, we need to wrap them in TARGET_EXPR.  I previously fixed
that in build_array_copy; we also need it in process_init_constructor.
After fixing that, I needed to adjust a few places to recognize the
VEC_INIT_EXPR even inside a TARGET_EXPR.  And prevent cp_fully_fold_init
from lowering VEC_INIT_EXPR too soon.  And handle COMPOUND_EXPR inside
TARGET_EXPR better.

	PR c++/104300
	PR c++/92385

gcc/cp/ChangeLog:

	* cp-tree.h (get_vec_init_expr): New.
	(target_expr_needs_replace): New.
	* cp-gimplify.cc (cp_gimplify_init_expr): Use it.
	(struct cp_fold_data): New.
	(cp_fold_r): Only genericize inits at end of fn.
	(cp_fold_function): Here.
	(cp_fully_fold_init): Not here.
	* init.cc (build_vec_init): Use get_vec_init_expr.
	* tree.cc (build_vec_init_expr): Likewise.
	* typeck2.cc (split_nonconstant_init_1): Likewise.
	(process_init_constructor): Wrap VEC_INIT_EXPR in
	TARGET_EXPR.

gcc/testsuite/ChangeLog:

	* g++.dg/cpp0x/initlist-array14.C: New test.