You can now write things like this:
```
inst(BUILD_STRING, (pieces[oparg] -- str)) { ... }
inst(LIST_APPEND, (list, unused[oparg-1], v -- list, unused[oparg-1])) { ... }
```
Note that array output effects are only partially supported (they must be named `unused` or correspond to an input effect).
For these the instr_format field uses IX instead of IB.
Register instructions use IX, IB, IBBX, IBBB, etc.
Also: Include the closing '}' in Block.tokens, for completeness
(These aren't used yet, but may be coming soon,
and it's easier to keep this tool the same between branches.)
Added a sanity check for all this to compile.c.
Co-authored-by: Irit Katriel <iritkatriel@yahoo.com>
Irit Katriel
Mark Shannon
Guido van Rossum
Zachary Ware