re PR c++/83817 (internal compiler error: tree check: expected call_expr, have aggr_init_expr in tsubst_copy_and_build, at cp/pt.c:17822)

	PR c++/83817
	* pt.c (tsubst_copy_and_build) <case CALL_EXPR>: If function
	is AGGR_INIT_EXPR rather than CALL_EXPR, set AGGR_INIT_FROM_THUNK_P
	instead of CALL_FROM_THUNK_P.

	* g++.dg/cpp1y/pr83817.C: New test.

From-SVN: r256726