Switch to our own version of SFML's audio components.

This change allows us to control the creation and destruction of the
AudioDevice object
Updated Squirrel to 3.0.5
Merge branch 'development'
Cleanup of changes to address issue #21

We keep our own slightly modified version of SFML audio code (in extlibs)
so we can control the creation and destruction of the AudioDevice object
Fix for 8-bit wav audio (and possibly others)
Bump to version 1.2.1