[Groff] margin macros

[Larry McVoy]

Hi, I have a partial answer to my earlier question about margin notes.
Here's what I came up with, these seem to work OK if you have left yourself
a 1.5 inch page offset.  They even complain when the margin note will cause
a page break.

.ev margin-ev
.       ps 8
.       vs 9
.       ft R
.ev
.de MS
.       ev margin-ev
.       di margin-di
.       sp .25
.       po .4i
.       ll .6i
..
.de ME
.       br
.       di 
.       ie (\\n[dn]+\\n[nl])>=(\\n[.p]-\\n[FM]) \{\
.               tm Margin message is too big at line \\n[.c]
.       \} 
.       el \{\
.               margin-di
.               sp -\\n[dn]u
.       \}
.       po
.       ll
.       ev
..