Fix gdbserver cross build.

The recent libiberty patch caused issues when cross building
gdbserver.  The Makefile ends invoking the build machine's "ar"
instead of the --host version:

  ar  ./libiberty.a \
	    ./regex.o (...)

  ar: illegal option -- .
  Usage: ar [emulation options] [-]{dmpqrstx}[abcfilNoPsSuvV] [member-name] [count] archive-file file...
	 ar -M [<mri-script]

The libiberty configure script does probe for and finds an appropriate
AR.  However, gdbserver's configure does not probe for AR and
overrides the AR used in the libiberty build by explicitly passing AR
to the sub-builds.

gdb/gdbserver/
2014-06-20  Marcus Shawcroft  <marcus.shawcroft@arm.com>

	* configure.ac: Invoke. AC_CHECK_TOOL(AR, ar).
	* Makefile.in (AR, AR_FLAGS): Define.
	* configure: Regenerate.
Vectorize gdbserver x86 debug register accessors

This commit makes gdbserver access the x86 debug register accessor
functions via the same function vector as GDB proper.  This removes
a chunk of conditional code that was previously in i386-{nat,low}.h
and leaves a single macro as the only GDB/gdbserver difference in
nat/i386-dregs.c.

gdb/
2014-06-20  Gary Benson  <gbenson@redhat.com>

	* i386-nat.h (debug_hw_points): Moved to nat/i386-dregs.c.
	(i386_dr_low_type): Moved to nat/i386-dregs.h.
	(i386_dr_low): Likewise.
	(i386_dr_low_can_set_addr): Moved to nat/i386-dregs.c.
	(i386_dr_low_set_addr): Likewise.
	(i386_dr_low_get_addr): Likewise.
	(i386_dr_low_can_set_control): Likewise.
	(i386_dr_low_set_control): Likewise.
	(i386_dr_low_get_control): Likewise.
	(i386_dr_low_get_status): Likewise.
	(i386_get_debug_register_length): Likewise.
	* nat/i386-dregs.h (i386_dr_low_type): Moved from i386-nat.h.
	(i386_dr_low): Likewise.
	* nat/i386-dregs.c (i386-low.h): Remove include.
	(i386-nat.h): Likewise.
	(nat/i386-dregs.h): New include.
	(i386_dr_low_can_set_addr): Moved from i386-nat.h.
	(i386_dr_low_set_addr): Likewise.
	(i386_dr_low_get_addr): Likewise.
	(i386_dr_low_can_set_control): Likewise.
	(i386_dr_low_set_control): Likewise.
	(i386_dr_low_get_control): Likewise.
	(i386_dr_low_get_status): Likewise.
	(i386_get_debug_register_length): Likewise.
	(debug_hw_points): Likewise.

gdb/gdbserver/
2014-06-20  Gary Benson  <gbenson@redhat.com>

	* i386-low.h (i386_dr_low_can_set_addr): Removed.
	(i386_dr_low_set_addr): Likewise.
	(i386_dr_low_get_addr): Likewise.
	(i386_dr_low_can_set_control): Likewise.
	(i386_dr_low_set_control): Likewise.
	(i386_dr_low_get_control): Likewise.
	(i386_dr_low_get_status): Likewise.
	(i386_get_debug_register_length): Likewise.
	* linux-x86-low.c (i386_dr_low_set_addr):
	Changed signature.  Made static.
	(i386_dr_low_get_addr): Likewise.
	(i386_dr_low_set_control): Likewise.
	(i386_dr_low_get_control): Likewise.
	(i386_dr_low_get_status): Likewise.
	(i386_dr_low): New global variable.
	* win32-i386-low.c (i386_dr_low_set_addr):
	Changed signature.  Made static.
	(i386_dr_low_get_addr): Likewise.
	(i386_dr_low_set_control): Likewise.
	(i386_dr_low_get_control): Likewise.
	(i386_dr_low_get_status): Likewise.
	(i386_dr_low): New global variable.