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

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

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

gcc/ChangeLog:

	* ifcvt.cc (cond_exec_changed_p): Change variable to bool.
	(last_active_insn): Change "skip_use_p" function argument to bool.
	(noce_operand_ok): Change return type from int to bool.
	(find_cond_trap): Ditto.
	(block_jumps_and_fallthru_p): Change "fallthru_p" and
	"jump_p" variables to bool.
	(noce_find_if_block): Change return type from int to bool.
	(cond_exec_find_if_block): Ditto.
	(find_if_case_1): Ditto.
	(find_if_case_2): Ditto.
	(dead_or_predicable): Ditto. Change "reversep" function arg to bool.
	(block_jumps_and_fallthru): Rename from block_jumps_and_fallthru_p.
	(cond_exec_process_insns): Change return type from int to bool.
	Change "mod_ok" function arg to bool.
	(cond_exec_process_if_block): Change return type from int to bool.
	Change "do_multiple_p" function arg to bool.  Change "then_mod_ok"
	variable to bool.
	(noce_emit_store_flag): Change return type from int to bool.
	Change "reversep" function arg to bool.  Change "cond_complex"
	variable to bool.
	(noce_try_move): Change return type from int to bool.
	(noce_try_ifelse_collapse): Ditto.
	(noce_try_store_flag): Ditto. Change "reversep" variable to bool.
	(noce_try_addcc): Change return type from int to bool.  Change
	"subtract" variable to bool.
	(noce_try_store_flag_constants): Change return type from int to bool.
	(noce_try_store_flag_mask): Ditto.  Change "reversep" variable to bool.
	(noce_try_cmove): Change return type from int to bool.
	(noce_try_cmove_arith): Ditto. Change "is_mem" variable to bool.
	(noce_try_minmax): Change return type from int to bool.  Change
	"unsignedp" variable to bool.
	(noce_try_abs): Change return type from int to bool.  Change
	"negate" variable to bool.
	(noce_try_sign_mask): Change return type from int to bool.
	(noce_try_move): Ditto.
	(noce_try_store_flag_constants): Ditto.
	(noce_try_cmove): Ditto.
	(noce_try_cmove_arith): Ditto.
	(noce_try_minmax): Ditto.  Change "unsignedp" variable to bool.
	(noce_try_bitop): Change return type from int to bool.
	(noce_operand_ok): Ditto.
	(noce_convert_multiple_sets): Ditto.
	(noce_convert_multiple_sets_1): Ditto.
	(noce_process_if_block): Ditto.
	(check_cond_move_block): Ditto.
	(cond_move_process_if_block): Ditto. Change "success_p"
	variable to bool.
	(rest_of_handle_if_conversion): Change return type to void.