a) Added sim_debug statements, formatted console messages.
b) Removed old debugging statements and redundant byte/word mask operations.
c) Added more device commands.
d) Added zx-200a and changed nulldev to return 0 vice 0xff.
e) Added commands and corrected RTYPE and RBYTE behavior so ISIS-II would boot.
f) Corrected device calls in SBC_reset, corrected get_mbyte and put_mbyte to
match control bits from ipc_cont.c.
These changes facilitate more robust parameter type checking and helps
to identify unexpected coding errors.
Most simulators can now also be compiled with a C++ compiler without
warnings.
Additionally, these changes have also been configured to facilitate easier
backporting of simulator and device simulation modules to run under the
simh v3.9+ SCP framework.
