INT 1A - SNAP.EXE 3.2+ - "SNAP_COPYTO" - COPY DATA TO RESIDENT SNAP PACKAGE
        AX = 6C04h
        STACK:  WORD    offset within SNAP data segment of dest (nonzero)
                WORD    segment of source buffer
                WORD    offset of source buffer
                WORD    number of bytes to copy
Return: AX = offset of byte after last one copied to destination
        STACK unchanged
Program: SNAP.EXE is a TSR written by IBM and Carnegie Mellon University
          which implements the Simple Network Application Protocol