* defs.h, utils.c: xrealloc takes PTR as first arg.

	* defs.h, utils.c:  xrealloc takes PTR as first arg.
	* defs.h:  Reword confusing comment about ANSI prototypes.
	* defs.h:  Some minor whitespace changes.
	* infrun.c (wait_for_inferior):  Compare int tmp to int 0,
	not NULL, which can be (void *).
	* tm-amix.h, tm-i386v4.h:  Add defines for setjmp/longjmp handling.
	* tm-i386v.h (SP_ARG0):  Define
	* xm-sysv4.h:  Back out of change for missing prototypes.
	* i386-tdep.c (get_longjmp_target):  Add function.