Version of IDE supported?

[Geoffrey Leach]

I'm working on cleaning up the Perl support of taglib. For various 
reasons, I'm beginning with taglib 1.5. For some reason, I assumed that 
this supported IDEv2.3.0, although I can't find this documented. 
However, in /taglib/mpeg/id3v2/frames/relativevolumeframe.cpp I find a 
reference to RVA2 frame type, which appears to be a v2.4.0 entity.

So, what's supported?

Thanks.