Update ssa_prop_visit_phi_fn callbacks to take a gimple_phi

Update ssa_prop_visit_phi_fn callbacks to take a gimple_phi

This corresponds to:
  [PATCH 10/89] Update ssa_prop_visit_phi_fn callbacks to take a gimple_phi
  https://gcc.gnu.org/ml/gcc-patches/2014-04/msg01216.html
from the original 89-patch kit

That earlier patch was approved by Jeff:
> OK when prerequisites have gone in.
in https://gcc.gnu.org/ml/gcc-patches/2014-05/msg00619.html

gcc/
	* tree-ssa-propagate.h (typedef ssa_prop_visit_phi_fn): Strengthen
	type of parameter from gimple to gimple_phi.

	* tree-complex.c (complex_visit_phi): Update signature of callback
	implementation accordingly.
	* tree-ssa-ccp.c (ccp_visit_phi_node): Likewise.
	* tree-ssa-copy.c (copy_prop_visit_phi_node): Likewise.
	* tree-vrp.c (vrp_visit_phi_node): Likewise.

	* tree-ssa-propagate.c (simulate_stmt): Add a checked cast to
	gimple_phi when invoking the ssa_prop_visit_phi callback.