Correct the behavior of SYSTEM(0) for D3 emulation
Previous Release Behavior
SYSTEM(0) was not coded for D3 emulation.
Current Release Behavior
As per the D3 documentation, SYSTEM(0) returns the last error number usually. This is broadly compatible with other emulations.
However, if the last error was caused by a LOCKED clause being taken on a READU, then SYSTEM(0), under D3 emulation, returns the port number of the process holding the lock.