[Groff] [heirloom] getting dashes when a line is requested

[Blake McBride]

Greetings,

Using the following:

.TS
l .
_
abcdefghijklmnopqrstuvwxyz
.TE


In groff, the line is unbroken (as is desired).  In heirloom, a bunch of
dashes are produced.  Each dash is separated by a small space.  In other
words, groff produced a _line_, and heirloom troff produces a _series of
dashes_.  Surely a line is desired.

Thanks.

Blake