* Makefile.in (SFILES OBS): Add serial.[co] & ser-hardwire.[co].

	* Makefile.in (SFILES OBS):  Add serial.[co] & ser-hardwire.[co].
	These implement a new serial line interface for talking to remote
	targets.
	* configure.in:  Link ser-hardwire.c to ser-unix.c for all hosts,
	EXCEPT go32, which gets ser-go32.c.
	* remote.c:  Use new serial interface.  More remote-xxx's to be
	converted later.
	* ser-bsd.c, ser-termios.c:  Removed.
	* serial.c:  New.  Implements common operations for all serial
	types.
	* ser-unix.c:  New.  Unix specific serial operations for various
	flavors of Unix (Posix, SysV, BSD).
	* serial.h:  Generic serial interface defs.
	* config/i386/go32.mh, config/i386/i386bsd.h,
	config/m68k/apollo68b.mh, config/sparc/sun4os4.mh:  Remove
	ser-bsd.o from XDEPFILES.  All the magic is now handled in
	configure.in.