Mach 3 support.

	Mach 3 support.
	* config.bfd (m88*-*-mach3*, mips*-dec-mach3*, mips*-*-mach3*):
	New targets.
	* configure.host (i[34]86-*-mach3*, ns32k-*-mach3*): Recognize
	"mach3" instead of "mach".
	(m88*-*-mach3*, mips*-dec-mach3*, mips*-*-mach3*): New hosts.
	* targets.c (m88kmach3_vec): New target vector.
	(bfd_target_vector): Add i386mach3_vec and m88kmach3_vec, but
	inside #if 0.
	* aoutx.h (some_aout_object_p) [MACH]: Recognize executables by
	checking for execute permission, instead of looking at entry
	point.
	* i386mach3.c: Update, define MACH, N_TXTOFF, N_TXTADDR,
	N_SHARED_LIB, don't include aout/*.h files, etc.
	* m88kmach3.c: New file, m88k Mach 3 target.
	* config/m88k-mach3.mt,	config/mips-mach3.mt: New files, target
	makefile fragments.
	* config/i386mach3.mh, config/m88kmach3.mh, config/mipsmach3.mh:
	New files, host	makefile fragments.
	* hosts/m88kmach3.h, hosts/mipsmach3.h: New files, host definitions.