gdbserver: remove support for Neutrino

This port has been unmaintained for years, remove it.

gdbserver/ChangeLog:

	* configure: Re-generate.
	* configure.ac: Remove srv_qnx test.
	* configure.srv: Remove nto case.
	* nto-low.cc, nto-low.h, nto-x86-low.cc: Remove.
	* remote-utils.c: Remove __QNX__-guarded code.

Change-Id: I8a1ad9c740a69352da1f6993778dbf951eebb22f