Approximate file correspondance:
	as680.c		main.c		main routines and pass1 driver
	as681.c		symt.c		symbol table manipulation routines
	as682.c		expr.c		routines for expression handling
	as683.c		pass1a.c	branch optimization pass
	as684.c		pass2.c		pass2 driver and main pass2 routines
	as685.c		misc.c		pass2 routines, effective address etc.
	N/A			dir.c		directive handling routines pass1, pass2,
							and conditional assembly
	N/A			mach.h		Define target machine

The main functionality changes are listed as comments near the
top of main.c.
