Use cross-plat IWavePlayer to eliminate loading times for sound players

[jonko0493]

This structurally changes the project a bit as we needed the ability to add native code. Everything else works the same.

Notable limitation: on Windows, you can play as many sounds at the same time as you like. However, on Mac and Linux, you can only play one sound at a time.

Also slipped in a couple of fixes to the script preview renderer, namely:

• Added SET_READ_FLAG as a command that prohibits graph edges (possibly need to rename that command to BACK), which fixes rendering in topic files and a few other places
• Sprite exits are handled after dialogue is advanced, so now the sprite renderer handles those on the following command

[WiIIiam278]

Looks (well, sounds!) really good, works a treat on Mac, so much faster. Did notice that voiced line references don't populate quite right on this for some reason, but that's probably unrelated.