Multiple font editor

[Eric Dean Tribble <tribble>]

When I built the line compositor initially, I wanted to simplify the
inner loop as much as possible just to make sure I was keeping all the
details straight.  I've thought of throwing the font computation back
into the main loop, but for the common display case of one run per
line (because it's all one font) there is hardly even any loop
overhead.  That may change when we get into version comparison and
such.  If so, the change is trivial.

dean