Merge gdb and gdbserver implementations for siginfo

Merge gdb and gdbserver implementations for siginfo

Extract the compatible siginfo handling from amd64-linux-nat.c and
gdbserver/linux-x86-low to a new file nat/amd64-linux-siginfo.c.

2016-02-02  Walfred Tedeschi  <walfred.tedeschi@intel.com>

gdb/ChangeLog:

	* nat/amd64-linux-siginfo.c: New file.
	* nat/amd64-linux-siginfo.h: New file.
	* Makefile.in (HFILES_NO_SRCDIR): Add nat/amd64-linux-siginfo.h.
	(amd64-linux-siginfo.o): New rule.
	* config/i386/linux64.mh (NATDEPFILES): Add amd64-linux-siginfo.o.
	* amd64-linux-nat.c (nat/amd64-linux-siginfo.h): New include.
	(compat_siginfo_from_siginfo, siginfo_from_compat_siginfo)
	(compat_x32_siginfo_from_siginfo, siginfo_from_compat_x32_siginfo)
	(compat_timeval, compat_sigval, compat_x32_clock, cpt_si_pid)
	(cpt_si_uid, cpt_si_timerid, cpt_si_overrun, cpt_si_status)
	(cpt_si_utime, cpt_si_stime, cpt_si_ptr, cpt_si_addr, cpt_si_band)
	(cpt_si_fd, si_timerid, si_overrun): Move to nat/amd64-linux-siginfo.c.

gdb/gdbserver/ChangeLog:

	* configure.srv (x86_64-*-linux*): Add amd64-linux-siginfo.o
	to srv_tgtobj.
	(i[34567]86-*-linux*): Add amd64-linux-siginfo.o
	to srv_tgtobj.
	* linux-x86-low.c [__x86_64__]: Include
	"nat/amd64-linux-siginfo.h".
	(compat_siginfo_from_siginfo, siginfo_from_compat_siginfo)
	(compat_x32_siginfo_from_siginfo, siginfo_from_compat_x32_siginfo)
	(compat_timeval, compat_sigval, compat_x32_clock, cpt_si_pid)
	(cpt_si_uid, cpt_si_timerid, cpt_si_overrun, cpt_si_status)
	(cpt_si_utime, cpt_si_stime, cpt_si_ptr, cpt_si_addr, cpt_si_band)
	(cpt_si_fd, si_timerid, si_overrun): Move from
	nat/amd64-linux-siginfo.c.
	* Makefile.in (amd64-linux-siginfo.o:): New rule.