Fixed bug that caused literal .sp to show up in output. (Thanks to

Fixed bug that caused literal .sp to show up in output. (Thanks to
Costin Stroie for reporting).

WARNING: One of the consequences of this change is that the
stylesheet no longer generates spaces at the end of certain lines.
I had it doing that as a sort of hack to prevent certain kinds of
problems in output. It seems like the hack my no longer be
necessary. But if I am wrong, this change may cause spaces to show
up at the beginning of some lines in "mixed content". If you see
those, then this change has introduced a regression, and I will
need to go back and figure out the right way to fix it (instead of
the kludgy way I was doing it before.

Also, instances like the following were showing up in some cases.

  .PP
  .sp

That is, a .PP macro immediately followed by a .sp macro. I can
think of no good read to ever generate that, and I am not sure why
it is getting generated. So I have taked the lazy way out and
caused the stylesheet to now strip out the .sp from all such
instances, leaving just the .PP