"""Combine similar index entries into an entry and subentries.
For example:
\item {foobar} (in module flotz), 23
\item {foobar} (in module whackit), 4323
becomes
\item {foobar}
\subitem in module flotz, 23
\subitem in module whackit, 4323
Note that an item which matches the format of a collapsable item but which
isn't part of a group of similar items is not modified.
"""
This results in a much more readable index, with less repitition of text;
especially for common method names.
