Tidy #include lists

Tidy #include lists

This commit tidies up the #include lists in {i386,amd64}-linux-nat.c,
removing headers that are no longer required and reordering some lines
so that both files roughly match.  Additionally, an unused definition
was removed from the middle of the #include list in i386-linux-nat.c.

gdb/
2014-07-11  Gary Benson  <gbenson@redhat.com>

	* amd64-linux-nat.c (gdbcore.h): Remove include.
	(regset.h): Likewise.
	(nat/linux-btrace.h): Likewise.
	(btrace.h): Likewise.
	(gdb_assert.h): Likewise.
	(string.h): Likewise.
	(sys/uio.h): Likewise.
	(sys/debugreg.h): Likewise.
	(sys/syscall.h): Likewise.
	(sys/procfs.h): Likewise.
	(sys/user.h): Likewise.
	(asm/ptrace.h): Likewise.
	(i386-nat.h): Likewise.
	* i386-linux-nat.c (i386-nat.h): Likewise.
	(regset.h): Likewise.
	(target.h): Likewise.
	(linux-nat.h): Likewise.
	(nat/linux-btrace.h): Likewise.
	(btrace.h): Likewise.
	(gdb_assert.h): Likewise.
	(string.h): Likewise.
	(sys/uio.h): Likewise.
	(sys/user.h): Likewise.
	(sys/procfs.h): Likewise.
	(sys/reg.h): Likewise.
	(sys/debugreg.h): Likewise.
	(ORIG_EAX): Remove definition.