Demote to sw watchpoint only in update_watchpoint.

	Demote to sw watchpoint only in update_watchpoint.
	* breakpoint.c (update_watchpoint): Change between software and
	hardware watchpoint for all kinds of watchpoints, not just
	read/write ones.  Determine b->exact value here instead of
	in watch_command_1.  Error out if there are not enough resources
	for a read or access hardware watchpoint.
	(watch_command_1): Remove logic of checking whether there are
	enough resources available, since update_watchpoint will do that
	work now.  Don't set b->exact here.  Catch exceptions thrown by
	update_watchpoint and delete the watchpoint.
	(can_use_hardware_watchpoint): Remove exact_watchpoints argument.
	Use target_exact_watchpoints instead.
	(delete_breakpoint): Notify observers only if deleted watchpoint
	has a breakpoint number assigned to it.