Improve error message in case of missing ]
Don't store thunks in a CrumbList

This e.g. makes ReadVal fail immediately on a parse error (in int mode).
New option to read Brainfuck code from a file
Add --nofinaltape option
Split DirectPrgmIO

This reverts a7787f0.
Char IO: Show prompts, but only on a mode (read/write) change
Merge branch 'pu/parser'
Merge branch 'pu/strict-cl'
Merge branch 'pu/cmdargs'
Merge branch 'pu/split-direct'