comint-prompt-read-only causes problems in Gnus message mode

[Harald Maier]

Hello all,

I have set the new option `comint-prompt-read-only' and I like it very
much. When I copy the prompt from the shell buffer and yank it to
other buffers mostly I don't have problems. Except in the Gnu
'Message' mode. Here you are *not able* to delete the inserted prompt.
'Message' mode always complains 'Text is read only'. In other modes
the inserted prompt too has the property 'read-only' but there it's
possible to delete the text (e.g. text-mode or the normal mail mode).

The only way to get rid of the inserted comint prompt is to save the
buffer and reopen it from the 'nndraft:drafts' group.

Harald