Add volume control int Windows through the mixer API (until XP) and the
EndpointVolume API (Vista and above). Add volume control in Linux
through ALSA.
Convert AudioManager to use shared_ptrs.
SDL_mixer is not in the standard SDL distribution. The mixing is now
done using regular SDL_Audio functions. AudioManager is converted to a
singleton and std::shared_ptrs are used for all Sound objects. Note that
for GCC "-std=c++11" might need to be added to the CMAKE_CXX_FLAGS.
You should no longer see non-error output with ES except for "cleanly shutting down".
The new log file is located in ~/.emulationstation/es_log.txt.
If you notice any performance degredation, please tell me!
