clean_key(): Override the standard LaTeX2HTML clean_key() to remove a
leading HTML tag, if present. This broke the indexes for the library
reference (at least) since many of the strings began with <code> or
something similar.
includes the string in the returned value instead of the dummy
filler character.
add_idx(): Override the latex2html function of the same name; this gets
the anchor properly embedded in the <dt> element, so the index
works in Grail too.
some defaults are set here, but mostly this allows the "\," command
to be used the way it is in the Python documentation.
All future documentation should probably be written with only ","
in the argument lists and not "\,".