Adds:
1) Simulator side execution of register update activities at an interval
specified in usecs. Rates in excess of 1000Hz should be achievable
for locally connected frontpanel applications.
2) New API for simulators to describe the register state available in
the simulator. If all of a the state which is potentially interesting
to front panel applications is always present in the variables
described by simh REG structures, then frontpanel API access to
that data can be more efficiently provided.
- added verification of the existence of simulator registers which they are referenced.
- sim_frontpanel API version checking to make sure that the invoking API and the simulator support the same capabilities.
- added the ability for a simulator to reference data in simh register data which is not in the set of registers defined in the default simh device (usually the CPU).
- added a simulator time reference relating to a set of register data which is provided.
- added example automatically creating a console terminal port from a simulator startup (front panel or not).
