GameCube Microphone Support

[Papermanzero]

Some GameCube Games need a microphone (Odama, Mario Party 6 etc.).
However the microphone and its settings are not available in the libretro core.

[gouchi]

Hi @Papermanzero ,

Now that RA can access to microphone per this commit.

It might be possible to add this feature in Libretro Dolphin as it has been update recently to upstream.

This feature could allow to play those games.

[cscd98]

Added in #415

[gouchi]

@Papermanzero Please make some test with latest update.

Thank you.

[Papermanzero]

I will do :-)