This tries to fold unconditionally and fixes some test cases.

gcc/ChangeLog:

2017-05-18  Robin Dapp  <rdapp@linux.vnet.ibm.com>

	* tree-ssa-propagate.c
(substitute_and_fold_dom_walker::before_dom_children):
	Always try to fold.



gcc/testsuite/ChangeLog:

2017-05-18  Robin Dapp  <rdapp@linux.vnet.ibm.com>

	* g++.dg/tree-ssa/ssa-dse-2.C: Fix testcase.
	* gcc.dg/pr35691-1.c: Likewise.
	* gcc.dg/pr35691-2.c: Likewise.
	* gcc.dg/tree-ssa/forwprop-16.c: Likewise.
	* gcc.dg/tree-ssa/pr52631.c: Likewise.
	* gcc.dg/tree-ssa/vrp23.c: Likewise.