Gemini Rue AGS Mac/Linux port fixes (rebased)

Replacement for pull #108

Here are all of the commits related to the Mac/Linux port of Gemini Rue on AGS.  Most of the real work is in the allegro4 branch https://github.com/humble/allegro4-geminirue/compare/4.4...humble

The Mac port follows the iOS port's style of blitting to an OpenGL texture.  
The Linux port is designed around private libraries, thus requiring nothing extra on the end-users system.. the Audio was "fixed" on linux by using SDL2 to handle the audio playback (thus it will use PulseAudio, alsa, or oss depending on the users setup). This was far simpler than getting a pulse audio backend in allegro 4.4 working.

The release binaries included with GeminiRue were built on
* Mac -  XCode 5, SDK10.8, targeting 10.6+.
* Linux - CentOS 6 32bit & 64bit chroot (via mock) ( https://github.com/OutOfOrder/OOOBuildSystem )