Documentation tweaks to help documentation systems (Doxygen + PHPDocumentor)

Documentation tweaks to help documentation systems (Doxygen + PHPDocumentor)
pick up the appropriate tags, and documentation blobs for classes. This is
the same as per r20769, but with the grouping changes (e.g. removing "@{{") omitted.
Please be advised that more related documentation tweaks may follow later - e.g.
Doxygen generates a log file of warnings that is 574 Kb in size, when run over
the just the trunk/phase3 code ... eek! Thankfully, much of that is just
whining about functions without documentation   ;-)