executor: use the size of the opcode arg to get multiplier
executor: use the size of the opcode arg to get multiplier

When loading a constant, select the multiplier based on the size of the
opcode argument. This is safer because we have existing code that declares
the constants of the wrong size.

jpakkane/orc,ijsf/OpenWebRTC-orc,ijsf/OpenWebRTC-orc,jpakkane/orc,ijsf/OpenWebRTC-orc,jpakkane/orc