INT 1A - SNAP.EXE 3.2+ - "SNAP_COPYFROM" - COPY DATA FROM RESIDENT SNAP PACKAGE
        AX = 6D04h
        STACK:  WORD    offset within SNAP data segment of source buffer
                WORD    segment of destination buffer
                WORD    offset of destination buffer
                WORD    number of bytes to copy
Return: AX = offset of byte after last one copied from source
        buffer filled
        STACK unchanged