qdoc has been modified to emit a compact list of the
classes that have one or more obsolete members. The
command is:

\generatelist obsoletecppmembers

This generates an index of all such classes,
where each class name is a link to the class's
subpage of obsolete members. A class's subpage
of obsolete members is also accessible from the
class's reference page, but now it is also
accessible from this index.

Also, The command shown has been added to the
page obsoleteclasses.html in the generated
output. This page already contains the index
of obsolete classes.

Currently, no such output is generated for
QML types and QML types with obsolete members.
But qdoc does accept commands for those:

\generatelist obsoleteqmltypes

and

\generatelist obsoleteqmlmembers

...but qdoc doesn't know what to do with
those commands yet.

Task-number: QTBUG-30270
Change-Id: If19a3b977f64c948e4bd6f14a9e0a287419baa8a
Reviewed-by: Jerome Pasion <jerome.pasion@digia.com>