Correctly match ranges in memchecks with ends.
Don't just forget other memchecks, arg.
Output less code per memcheck.

Somehow this also fixed a bug with memchecks that didn't hit, but I don't
know why.  Reverting and making them far jumps doesn't help.... strange.

Anyway, this should be less code which is good.
Merge pull request #2625 from unknownbrackets/debugger

Fix some memcheck bugs