gcse: Change return type of predicate functions from int to bool

gcse: Change return type of predicate functions from int to bool

Also change some internal variables and function arguments from int to bool.

gcc/ChangeLog:

	* gcse.cc (expr_equiv_p): Change return type from int to bool.
	(oprs_unchanged_p): Change return type from int to void
	and adjust function body accordingly.
	(oprs_anticipatable_p): Ditto.
	(oprs_available_p): Ditto.
	(insert_expr_in_table): Ditto.  Change "antic_p" and "avail_p"
	arguments to bool. Change "found" variable to bool.
	(load_killed_in_block_p): Change return type from int to void and
	adjust function body accordingly.  Change "avail_p" argument to bool.
	(pre_expr_reaches_here_p): Change return type from int to void
	and adjust function body accordingly.
	(pre_delete): Ditto.  Change "changed" variable to bool.
	(pre_gcse): Change return type from int to void
	and adjust function body accordingly. Change "did_insert" and
	"changed" variables to bool.
	(one_pre_gcse_pass): Change return type from int to void
	and adjust function body accordingly.  Change "changed" variable
	to bool.
	(should_hoist_expr_to_dom): Change return type from int to void
	and adjust function body accordingly.  Change
	"visited_allocated_locally" variable to bool.
	(hoist_code): Change return type from int to void and adjust
	function body accordingly.  Change "changed" variable to bool.
	(one_code_hoisting_pass): Ditto.
	(pre_edge_insert): Change return type from int to void and adjust
	function body accordingly.  Change "did_insert" variable to bool.
	(pre_expr_reaches_here_p_work): Change return type from int to void
	and adjust function body accordingly.
	(simple_mem): Ditto.
	(want_to_gcse_p): Change return type from int to void
	and adjust function body accordingly.
	(can_assign_to_reg_without_clobbers_p): Update function body
	for bool return type.
	(hash_scan_set): Change "antic_p" and "avail_p" variables to bool.
	(pre_insert_copies): Change "added_copy" variable to bool.