Avoid potential name space collision for the global variables PC, SP and BC
when readline is dynamically loaded. For some unknown reason, ncurses
exports these internal variables which may be needed in the context of
how ncurses is used by readline implementations. In any case, these
variable names are common in simulators, so there is an undesired
interaction between simulator internal variables and the simplest
solution is to rename these simulator global variables where they exist.
Another alternative is to merely declare these variables static when
they happen to only be referenced in a single simulator source module.
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.
