WIP player for libuade

libuade is the libraryized version of UADE, the Amiga deliplayer.
libuade is currently under development, and isn't available in any
stable release. This WIP library is designed to be used with libuade
as of 2013/10/11, but may need changes for later releases.
MDXMini, PMDMini: use nonprefixed functions

Let the Player classes extend the modules so that the functions are
available nonprefixed. Also follow the UADE style of calling wrapped
C functions - non-namespced, and always called with parens, to make it
clear when something is a C function versus when it's native Ruby code.

e.g. it looks better and is clearer to do:

mdx_open(mini, filename, dirname)

Than:

MDXMini.mdx_open mini, filename, dirname