Convert amd64-linux target descriptions

Convert amd64-linux target descriptions

This patch changes amd64-linux target descriptions so that they can be
dynamically generated in both GDB and GDBserver.

gdb/gdbserver:

2017-09-05  Yao Qi  <yao.qi@linaro.org>

	* Makefile.in (arch-amd64.o): New rule.
	* configure.srv: Append arch-amd64.o.
	* linux-amd64-ipa.c: Include common/x86-xstate.h.
	(get_ipa_tdesc): Call amd64_linux_read_description.
	(initialize_low_tracepoint): Don't call init_registers_x32_XXX
	and init_registers_amd64_XXX.
	* linux-x86-low.c (x86_linux_read_description): Call
	amd64_linux_read_description.
	(x86_get_ipa_tdesc_idx): Call amd64_get_ipa_tdesc_idx.
	(initialize_low_arch): Don't call init_registers_x32_XXX and
	init_registers_amd64_XXX.
	* linux-x86-tdesc-selftest.c: Declare init_registers_amd64_XXX
	and tdesc_amd64_XXX.
	[__x86_64__] (amd64_tdesc_test): New function.
	(initialize_low_tdesc) [__x86_64__]: Call init_registers_x32_XXX
	and init_registers_amd64_XXX.
	* linux-x86-tdesc.c: Include arch/amd64.h.
	(xcr0_to_tdesc_idx): New function.
	(i386_linux_read_description): New function.
	(amd64_get_ipa_tdesc_idx): New function.
	* linux-x86-tdesc.h (amd64_get_ipa_tdesc_idx): Declare.
	(amd64_get_ipa_tdesc): Declare.

gdb:

2017-09-05  Yao Qi  <yao.qi@linaro.org>

	* amd64-linux-tdep.c: Include arch/amd64.h.  Don't include
	features/i386/*.c.
	(amd64_linux_read_description): Call
	amd64_create_target_description.
	* arch/amd64.c: New file.
	* arch/amd64.h: New file.
	* configure.tgt (x86_64-*-linux*): Append amd64.o.
	* Makefile.in (ALL_64_TARGET_OBS): Append amd64.o.