Various gimple to gimple_call conversions in IPA

Various gimple to gimple_call conversions in IPA

This corresponds to:
  [PATCH 56/89] Various gimple to gimple_call conversions in IPA
  https://gcc.gnu.org/ml/gcc-patches/2014-04/msg01179.html
from the original 89-patch kit

That earlier patch was approved by Jeff:
> OK once prereqs go in.
in https://gcc.gnu.org/ml/gcc-patches/2014-05/msg00857.html

gcc/
	* ipa-prop.c (detect_type_change_from_memory_writes): Require a
	gimple_call rather than a plain gimple.
	(detect_type_change): Likewise.
	(detect_type_change_ssa): Likewise.
	(compute_complex_assign_jump_func): Likewise.
	(compute_complex_ancestor_jump_func): Likewise.
	(compute_known_type_jump_func): Likewise.
	(determine_locally_known_aggregate_parts): Likewise.
	(ipa_compute_jump_functions_for_edge): Strengthen local "call" to
	a gimple_call; add checked cast to gimple_phi.
	(ipa_note_param_call): Require a gimple_call rather than a plain
	gimple.
	(ipa_analyze_indirect_call_uses): Likewise.
	(ipa_analyze_virtual_call_uses): Likewise.
	(ipa_analyze_call_uses): Likewise.
	(ipa_analyze_stmt_uses):Add checked cast to gimple_call.

	* tree-ssa-pre.c (eliminate_dom_walker::before_dom_children):
	Replace use of is_gimple_call with dyn_cast<gimple_call> and a
	new local "call_stmt".