Snapshot 23w11b

• asm32 (internal): check that mod-r/m-size was called before emitting a ModR/M byte

• asm32: emit 32-bit NEXT in 32-bit mode

• asm32: Implement shift instructions

• Document the internals of does>

• go32: Fix the alter-0 check

How did this work before??? Why was a small stack underflow the only
symptom?

• Show input position on exception

• asm32: Implement movzx

• fed: Make downwards scrolling faster

Going to the end of the file (or a search result) used to do it one line
at a time, rendering each step. This became an annoyingly slow animation
the 100th time you saw it on a long file.

• fed: Implement C and D (change/delete to end of line)

• go32: Coming back to 16-bit mode.