Determines what to do with comint output.
If nil, do nothing.
If the symbol `filter', then filter all SGR control sequences.
If anything else (such as t), then translate SGR control sequences
into text properties.
In order for this to have any effect, `ansi-color-process-output' must
be in `comint-output-filter-functions'.
This can be used to enable colorized ls --color=yes output
in shell buffers. You set this variable by calling one of:
M-x ansi-color-for-comint-mode-on
M-x ansi-color-for-comint-mode-off
M-x ansi-color-for-comint-mode-filter