AUv3 updateHostDisplay with parameterInfoChanged

So I noticed that the JUCE AUv3 implementation currently doesn’t do anything when calling updateHostDisplay(), with the ChangeDetails::parameterInfoChanged flag, so I took a shot at implementing it myself (see here).

This is my first time working with AudioUnit code at this level, so I’d appreciate any feedback. Also, it would be nice if this sort of thing could be added to mainline JUCE at some point down the road (@reuk).