Remove `^A' and `^B' characters from comint output.
Bash uses these characters as internal quoting characters in its
prompt. Due to a bug in some bash versions (including 2.03,
2.04, and 2.05b), they may erroneously show up when bash is
started with the `--noediting' option and Select Graphic
Rendition (SGR) control sequences (formerly known as ANSI escape
sequences) are used to color the prompt.
This function can be put on `comint-preoutput-filter-functions'.
(fn STRING)