Syntax: <label> OPWORD <word-length number>
Operation: Equate a value to an A-trap instruction. The OPWORD
directive associates a given A-trap name to its trap number.
All A-traps are values with the hexidecimal format $Axxx.
The OPWORD directive must be followed by a number or
numeric equation. Note that the assembler does not check the
value for the appropriate A-trap range, so the directive could
be used for asigning other word-length values if so desired.