[mew-int 2646] Longlines-mode in draft mode

[Harald Hanche-Olsen]

First, thanks for format=flowed support.

I tried turning on longlines-mode in mew-draft-mode-hook, but then 
the header becomes corrupted. It gets even worse if you try C-c C-o 
while longlines-mode is on.

How hard would it be to detect longlines-mode (a) when the header is 
created and (b) when mew-draft-set-case is run, and to disable it 
temporarily while those operations run?

I worry a bit that this request might baloon into a requirement for 
longlines-mode detection and avoidance in more places than you'd care 
to think about, but if the consequences in the code are limited, it 
would be worth it.

- Harald