[Groff] List element spacing in MOM

[Blake McBride]

Greetings,

I think space between list items should be controlled by .PARA_SPACE.  But
rather than breaking everything out there, perhaps there should be a new
macro called .LIST_SPACE that works like .PARA_SPACE but for lists.  Without
this macro, a user is forced to create their own macro which encapsulates
.ITEM in order to achieve this (likely common) effect.

Blake McBride