* breakpoint.c (update_watchpoint): Skip creating locations and
reading the selected frame if there's no execution.
(bpstat_stop_status): Use is_hardware_watchpoint. If not
stopping, update watchpoints and the global location list, instead
of removing and inserting all breakpoints.
(breakpoint_address_is_meaningful): Hardware watchpoints also have
a meaningful target address.
(watchpoint_locations_match): New.
(breakpoint_locations_match): New.
(watch_command_1): Create the watchpoint breakpoint without any
location initially. Use update_watchpoint to create the
watchpoint locations.
(update_global_location_list): Use breakpoint_locations_match, so
watchpoint locations are handled too. Also detect duplicate
watchpoint locations.