Changes for Irix 4.0, tested this time:

Changes for Irix 4.0, tested this time:
	* s/irix4-0.h: Get rid of our fake definitions for setpgrp and
	getpgrp.
	* callproc.c (Fcall_process): Go ahead and use the USG calling
	convention for setpgrp.
	* ymakefile (pre-crt0.o): Add rule for this.  Perhaps it will help
	separate-source-directory compilation.
	* emacs.c (shut_down_emacs): Some USG systems #define
	EMACS_HAVE_TTY_PGRP; call getpgrp as appropriate for such systems.
	* sysdep.c (sys_suspend): Call getpgrp as appropriate for USG and
	non-USG.
	* process.c [IRIX] (create_process): Don't put child in process
	group zero before opening the tty; Irix is like USG in this
	regard.