node-sdlmixer experiment

This is an experiment to get sdlmixer working together with nodejs.

Note: since I am completely new to nodejs addon development, this
is currently a very bad example of coding it.


Requirements for compilation:
- nodejs
- node-waf
- SDL-dev
- SDL_mixer-dev

tested on ubuntu 11.04 (64bit) with:
*) installing nodejs
*) sudo apt-get install libsdl1.2-dev
*) sudo apt-get install libsdlmixer1.2-dev