Fix up the RVA2 handling. I'm still not thrilled with the API, but this

Fix up the RVA2 handling.  I'm still not thrilled with the API, but this
should be functional enough to hold over to the next binary
incompatible change and has a minimum of differences to the previous
API.

I did a slightly nasty hack so that the API docs will see just methods
with an optional argument, but those are actually two separate methods
(for BC).

Brian, please feel free to take a look at this prior to 1.4 going out.

BUG:107025

git-svn-id: svn://anonsvn.kde.org/home/kde/trunk/kdesupport/taglib@437115 283d02a7-25f6-0310-bc7c-ecb5cbfe19da