Directly call i386-dregs functions

Directly call i386-dregs functions

Three target_ops functions in i386-nat.c call other local target_ops
functions.  This commit changes those functions to call the functions
in i386-dregs.c directly.

gdb/
2014-06-19  Gary Benson  <gbenson@redhat.com>

	* i386-nat.c (i386_stopped_by_watchpoint):
	Use i386_dr_stopped_by_watchpoint.
	(i386_insert_hw_breakpoint): Use i386_dr_insert_watchpoint.
	(i386_remove_hw_breakpoint): Use i386_dr_remove_watchpoint.