scp.c,scp.h - Gave priority to a command message handler to determine what values result in displayed messages and exported run_cmd_message for use by simulators which add simulator specific BOOT commands which leverage the run_cmd logic and should also leverage the run_cmd_message for message display
VAX/vax610_sysdev.c, vax730_sys.c, vax750_cmi.c, vax780_sbi.c - Added BOOT command message dispatch to run_cmd_message for simulators which perform preprocessing on BOOT activities but otherwise then dispatch to run_cmd.
