(i[34]86-*-mach3*, i[34]86-*-osf1mk*, mips-*-mach3*, m88*-*-mach3*, ns32k-*-mach3*): Recognize. * Makefile.in (gdb-stop): New target. * gdb-stop.c: New file, utility to gets attention of waiting GDBs in Mach 3.