With the advent of longlines-mode it seems highly useful to have this  
mode directly available from the Options menu, and at least have a  
simple way to turn it on automatically in all text modes, just like  
auto fill. This could be done as in the enclosed patch. Of course  
there would be more generic ways, integrating the auto fill and  
longlines toggle functions, etc. - but probably not worth the hassle.

Also, can I suggest to turn on longlines-wrap-follows-window-size by  
default? Longlines is very much a matter of altering the way text is  
displayed (rather than actually modifying the buffer as saved to  
disk). Therefore I think it would be very sensible to link it to the  
window size by default rather than to a fixed line length. (This  
change is not included in the patch.)