Fixed VMS Build of DEBUG simulators
Fixed bug under Asynch I/O where I/O completion did not delay the appropriate time before passing back device status to a simulator.  Found by Sergey Oboguev.
- Changed asynch queue insertion and removal to use a lock free algorithm based only on InterlockedCompareExchangePointer.  We can now use this lock free approach on IA64 host systems as well.

- Removed flawed logic which assumed that sim_interval was meaningful when referenced by an asynchronous thread.
- Adjust the event_time of events removed from the asynch queue to account for the average time spent on the queue before the event was noticed by the instruction execution thread.
- Added a sim_activate_notbefore function which specifies an rtime which is the earliest time the event should fire.
- Changed the 'wakeup from idle' logic to force an immediate asynch queue check if the wakeup was not due to a timeout (i.e. it was due to an asynch queue insertion).
- Fixed the descrip.mms to build asynchronous support on AXP and IA64 VMS with kernel threads enabled
Added missing synchronization when dispatching asynchronous calls.  From Sergey Oboguev
HP2100 update from Dave Bryan
Extensive Control Flow Enhancements:

Added Message Suppression flag for status values, including providing a -Q option to the RETURN command to return with a message suppressed status
Added Do command file default extension of .sim (from Dave Bryan)
Added -O option to DO command file invocation which causes the caller's ON state and actions to be inherited in the newly called DO command file
Added Command Line expansion to include a %* which expands to the whole set of arguments (%1 ... %9)
Relaxed Command Line argument substitution (delimited by %'s) which cause environment variable lookups to first lookup the literal name provided and if that fails, lookup the name upcased.
Added a SIM_VERIFY special Command Line expansion variable which expands to "-V" when command echoing is active
Added a SIM_MESSAGE special Command Line expansion variable which expands to "-Q" when error message display is suppressed
Added Command Aliasing, which causes the initial token on a command line to be looked up in the environment variable table, and if it exists to substitute the expansion for the initial token.
Changed environment variable defining (with SET ENV variable=value) to always upcase the variable name.
Added SHIFT command which shifts the numbered argument variables %1 ... %9 to the left by one (%1 becomes what was %2, etc.)
Added CALL command which will call a routine (label) in the currently executing command file
Added SET VERIFY and SET NOVERIFY commands which enable or disable DO command echoing
Added SET MESSAGE and SET NOMESSAGE commands which globally enable or disable the display of status messages when commands (or Do Commands) return with unsuccessful status
Added SET ON INHERIT and SET ON NOINHERIT to globally enable inheritance of ON state and actions when DO commands are invoked
Added PROCEED and IGNORE commands which are do nothing but return success.  These can be used in specific ON actions to possibly ignore particular return status values
Added DO command file line number to error messages which are displayed while processing DO command files
Expanded the DO command nesting level to 20 to potentially allow for more nesting due to the extensive use of CALL commands are used
Fixed Asynch I/O issues which may leave pending asynch I/O in limbo when device resets happen (found by Sergey Oboguev)
Partial merge from master branch
Finish Merge branch 'master' into HP2100Extensions

Conflicts:
	scp.c
	sim_defs.h