gdb/

gdb/
	Fix repeated rwatch output.
	* amd64-linux-nat.c (amd64_linux_dr_set, amd64_linux_dr_set_control)
	(amd64_linux_dr_set_addr, amd64_linux_dr_reset_addr)
	(amd64_linux_dr_get_status): New comments.
	(amd64_linux_dr_unset_status): New function.
	(_initialize_amd64_linux_nat): Install it.
	* i386-linux-nat.c (i386_linux_dr_get, i386_linux_dr_set)
	(i386_linux_dr_set_control, i386_linux_dr_set_addr)
	(i386_linux_dr_reset_addr, i386_linux_dr_get_status): New comments.
	(i386_linux_dr_unset_status): New function.
	(_initialize_i386_linux_nat): Install it.
	* i386-nat.c (I386_DR_WATCH_MASK): New macro.
	(I386_DR_WATCH_HIT): Use I386_DR_WATCH_MASK.
	(i386_insert_aligned_watchpoint): Call i386_dr_low.unset_status.
	* i386-nat.h (struct i386_dr_low_type): Extend comments for
	set_control, set_addr, reset_addr and get_status.  New unset_status.
	* breakpoint.c (update_watchpoint): Extend the comment.

gdb/testsuite/
	* gdb.base/watchpoint-hw-hit-once.exp,
	gdb.base/watchpoint-hw-hit-once.c: New.