SCP: Added const declarations to various APIs to reflect the appropriate usage.  Moved parameter values for run_cmd and exdep_cmd to scp.h
SCP: Added a Remote Console Master Mode.

This capability will allow a GDB RSB stub to be created to support dynamic debugging of code running in a simulator.

This capability will also allow a complete front panel emulation system to operate a simulator.

This capability is engaged in a simulator by:
     sim> set remote telnet=remoteconsoleport#
     sim> set console telnet=consoleport#
     sim> set remote master

Master mode will provide a TCP session which accepts SCP commands that allow full control of the simulator.