functions handling composite types and sets, various minor cleanups.

FUNCTION command.  Guard against trying to load a directory.  Update
documentation some.

ecpg reference page still needs formatting.

No big deal; fixed lots of other markup at the same time.
Bigest change: make sure there is no whitespace
 in front of <term> contents.
This will probably help the other output types too.

 of Norm's Modular Style Sheets and jade/docbook.
From Vince Vielhaber <vev@michvhf.com>.