comint: long lines truncated

[Ilya N. Golubev]

`comint.el' versions since revision 1.14 of 2006/05/25 02:49:47 -0
unconditionally add `TERM=dumb' to environment of all processes they
start.  Programs using readline, including bash 3.1 with their bundled
readline libraries, with this setting incorrectly truncate long input
lines.  This may be reproduced with inserting long enough command in
comint mode buffer and calling `comint-send-input'.  For `echo' with
single argument, string of 256 `.'s as arg bash process outputs part
of them, and for the rest of them outputs

bash: ................: command not found

This does not even depend on what libraries were linked to readline.
They may be from `libncurses5-5.3-1.20040125.4mdk' or
`libtermcap2-2.0.8-35mdk' packages, it is always the same.

With `TERM=emacs' (set manually) these programs would behave in comint
buffers normally, process commands of arbitrary length.  This is how
`comint.el' would set it before revision 1.13.  It avoided hitting
this bug.