breakpoint: Make is_*point functions return bool

breakpoint: Make is_*point functions return bool

This includes changing the FILTER parameters of two functions
accordingly.  I also tried to normalize the function comments to our
current standards.

gdb/ChangeLog:

	* breakpoint.c (is_hardware_watchpoint): Remove
	forward-declaration.
	(is_masked_watchpoint): Change return type to bool.
	(is_tracepoint): Likewise.
	(is_breakpoint): Likewise.
	(is_hardware_watchpoint): Likewise.
	(is_watchpoint): Likewise.
	(is_no_memory_software_watchpoint): Likewise.
	(is_catchpoint): Likewise.
	(breakpoint_1): Make FILTER parameter's return type bool.
	is_masked_watchpoint): Change return type to bool.
	(save_breakpoints): Make FILTER parameter's return type bool.
	* breakpoint.h (is_breakpoint): Change return type to bool.
	(is_watchpoint): Likewise.
	(is_catchpoint): Likewise.
	(is_tracepoint): Likewise.