Synthetic opcodes are composed of a 16 bit opcode followed by
operands.  All operands will be aligned appropriately.  Operands taking 16 or
fewer bits in the 68k instruction stream will NEVER be extended to 32 bits
in the synthetic stream.

If this instruction ends a block and has one or more known destination
blocks, the synthetic opcode is immediately followed by pointers to
the synthetic code in those blocks.

Next come any 32 bit operands not mentioned in the 68k description
file (eg, return addresses for jsrs).

Next come all 32 bit operands explicitly mentioned in the 68k
description file, in "field number" order (eg, $2.u precedes $4.s, etc.)

Finally we have all 16 bit operands, also in "field number" order.