I think we should make yet few related changes:
* Change meaning of jump offsets. They should count not bytes, but code units (16-bit words). This will extend the range addressed by short commands (from 256 bytes to 256 words) and simplify ceval.c.
* Change f_lasti, tb_lasti etc to count code units instead of bytes.
* Change disassembler to show addresses in code units, not bytes.
These changes break compatibility (already broken by switching to 16-bit bytecode). The first one breaks compatibility with compiled bytecode and needs incrementing the magic number. That is why I think we should do this in this issue.
What is better, provide one large patch or separate simpler patches for every stage?