Some library names are keyed off of the class, and then have sub-entries for members.
Some are keyed off the member, and have sub-entries for the classes with that member.
Some names are listed both ways, some names are listed neither way.

Sometimes constructors are listed as

bad_exception
bad_exception, 1234

Sometimes constructors are listed as

basic_filebuf
constructor, 1234

We should pick rules for what goes in this index, and follow them.