re PR c++/83556 (ICE in gimplify_expr, at gimplify.c:12004)

re PR c++/83556 (ICE in gimplify_expr, at gimplify.c:12004)

	PR c++/83556
	* tree.c (replace_placeholders_r): Pass NULL as last argument to
	cp_walk_tree instead of d->pset.  If non-TREE_CONSTANT and
	non-PLACEHOLDER_EXPR tree has been seen already, set *walk_subtrees
	to false and return.
	(replace_placeholders): Pass NULL instead of &pset as last argument
	to cp_walk_tree.

	* g++.dg/cpp0x/pr83556.C: New test.

From-SVN: r256086