Add "Audio.MusicGetFilepath" and "Audio.MusicGetFilepathArguments"

[SpencerlyEverly]

Today, I made a pull request with new functions added: "Audio.MusicGetFilepath" and "Audio.MusicGetFilepathArguments"!

With the functions, you can now see what music is currently playing on the engine, along with getting the SDL Mixer X arguments at the end! The functions should support all of these instances:

• Level Music (Including custom music on slot 24)
• World Music (Including, which isn't on the official branch yet, custom music on slot 17)
• Special Music (P-Switch, Stopwatch, Credits)
• Music played when sections are seized (Using "Audio.SeizeStream", "Audio.MusicOpen", and "Audio.MusicPlay" in that order)
• Music played with the Lua function "Audio.MusicChange" (Though the function is just replace the custom music ID filepath and play it)

Here's the function information below:

• Audio.MusicGetFilepath(shouldHaveArgumentsOrBlank): Gets the current playing music on the engine. If "shouldHaveArgumentsOrBlank" is false or not specified, any SDL Mixer X arguments at the end of the filepath will be removed.
• Audio.MusicGetFilepathArguments(): Gets the current playing music's SDL Mixer X arguments located at the end of the filepath.

Hope this pull request gets accepted!