re PR tree-optimization/56029 (ICE: verify_gimple failed, location references block not in block tree)

	PR tree-optimization/56029
	* tree-phinodes.c (reserve_phi_args_for_new_edge): Set
	gimple_phi_arg_location for the new arg to UNKNOWN_LOCATION.

	* g++.dg/torture/pr56029.C: New test.

From-SVN: r195304