function: Change return type of predicate function from int to bool

function: Change return type of predicate function from int to bool

Also change some internal variables to bool and some functions to void.

gcc/ChangeLog:

	* function.h (emit_initial_value_sets):
	Change return type from int to void.
	(aggregate_value_p): Change return type from int to bool.
	(prologue_contains): Ditto.
	(epilogue_contains): Ditto.
	(prologue_epilogue_contains): Ditto.
	* function.cc (temp_slot): Make "in_use" variable bool.
	(make_slot_available): Update for changed "in_use" variable.
	(assign_stack_temp_for_type): Ditto.
	(emit_initial_value_sets): Change return type from int to void
	and update function body accordingly.
	(instantiate_virtual_regs): Ditto.
	(rest_of_handle_thread_prologue_and_epilogue): Ditto.
	(safe_insn_predicate): Change return type from int to bool.
	(aggregate_value_p): Change return type from int to bool
	and update function body accordingly.
	(prologue_contains): Change return type from int to bool.
	(prologue_epilogue_contains): Ditto.