Merge pull request #274 from Zegeri/development

Fix counters, non-transparent pictures and others
Don't load music files based on their extension and detect the file format instead. Fixes #74
Merge pull request #275 from fdelapena/master

Detect music format and don't guess it from file extension. Fixes #74
Add SDL_mixer 1.2 compatibility
Merge pull request #276 from fdelapena/master

Add SDL_mixer 1.2 compatibility
Improve erased events
Prettify Game_Map::IsPassable