Audio: Replace SFML solution by using OpenAL directly

This is a major change in the Audio module that comes with
many changes throughout the codebase and dependency list.
The main gist is that we're finally nuking the last pieces
of SFML from the project. sfml-audio brought with itself
unneeded and big dependencies (libsndfile, libvorbisenc)
while at the same time limiting the amount of audio formats
mkxp can support (eg. we now get mp3 for free, and wma/midi
can be implemented by extending SDL_sound directly).

The increased control gained by interfacing with OpenAL directly
will also allow for easy integration of a dedicated audio
stretcher (librubberband), as well as enable us to implement
looped ogg vorbis (via the 'LOOPSTART'/'LOOPLENGTH' tags),
as required by RGSS2, in the future.

The FileSystem class has had its SFML parts removed.
Aditionally, audio file extensions to be supplemented are
now automatically detected based on how SDL_sound was
built (ie. if no mp3 support was built, mkxp won't try
to look for *.mp3 files). The final used extension
can be optionally returned by 'openRead' calls so
SDL_sound and SDL2_image can immediately choose the
right decoder.

The OpenAL context is created and destroyed in main.cpp
along side the GL context.

src/main.cpp

@@ -20,10 +20,12 @@
 */
 
 #include "glew.h"
+#include <alc.h>
 
 #include "SDL.h"
 #include "SDL_image.h"
 #include "SDL_ttf.h"
+#include <SDL_sound.h>
 
 #include "sharedstate.h"
 #include "eventthread.h"
@@ -77,7 +79,7 @@ int rgssThreadFun(void *userdata)
 {
 	RGSSThreadData *threadData = static_cast<RGSSThreadData*>(userdata);
 	SDL_Window *win = threadData->window;
-	SDL_GLContext ctx;
+	SDL_GLContext glCtx;
 
 	/* Setup GL context */
 	SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER, 1);
@@ -85,9 +87,9 @@ int rgssThreadFun(void *userdata)
 	if (threadData->config.debugMode)
 		SDL_GL_SetAttribute(SDL_GL_CONTEXT_FLAGS, SDL_GL_CONTEXT_DEBUG_FLAG);
 
-	ctx = SDL_GL_CreateContext(win);
+	glCtx = SDL_GL_CreateContext(win);
 
-	if (!ctx)
+	if (!glCtx)
 	{
 		rgssThreadError(threadData, QByteArray("Error creating context: ") + SDL_GetError());
 		return 0;
@@ -96,7 +98,7 @@ int rgssThreadFun(void *userdata)
 	if (glewInit() != GLEW_OK)
 	{
 		rgssThreadError(threadData, "Error initializing glew");
-		SDL_GL_DeleteContext(ctx);
+		SDL_GL_DeleteContext(glCtx);
 		return 0;
 	}
 
@@ -110,7 +112,7 @@ int rgssThreadFun(void *userdata)
 	if (!GLEW_VERSION_2_0)
 	{
 		rgssThreadError(threadData, "At least OpenGL 2.0 is required");
-		SDL_GL_DeleteContext(ctx);
+		SDL_GL_DeleteContext(glCtx);
 		return 0;
 	}
 
@@ -121,7 +123,7 @@ int rgssThreadFun(void *userdata)
 		{
 			rgssThreadError(threadData, QByteArray("Required GL extension \"")
 			                            + reqExt[i] + "\" not present");
-			SDL_GL_DeleteContext(ctx);
+			SDL_GL_DeleteContext(glCtx);
 			return 0;
 		}
 	}
@@ -130,6 +132,28 @@ int rgssThreadFun(void *userdata)
 
 	DebugLogger dLogger;
 
+	/* Setup AL context */
+	ALCdevice *alcDev = alcOpenDevice(0);
+
+	if (!alcDev)
+	{
+		rgssThreadError(threadData, "Error opening OpenAL device");
+		SDL_GL_DeleteContext(glCtx);
+		return 0;
+	}
+
+	ALCcontext *alcCtx = alcCreateContext(alcDev, 0);
+
+	if (!alcCtx)
+	{
+		rgssThreadError(threadData, "Error creating OpenAL context");
+		alcCloseDevice(alcDev);
+		SDL_GL_DeleteContext(glCtx);
+		return 0;
+	}
+
+	alcMakeContextCurrent(alcCtx);
+
 	SharedState::initInstance(threadData);
 
 	/* Start script execution */
@@ -140,7 +164,10 @@ int rgssThreadFun(void *userdata)
 
 	SharedState::finiInstance();
 
-	SDL_GL_DeleteContext(ctx);
+	alcDestroyContext(alcCtx);
+	alcCloseDevice(alcDev);
+
+	SDL_GL_DeleteContext(glCtx);
 
 	return 0;
 }
@@ -155,6 +182,7 @@ int main(int, char *argv[])
 	if (SDL_Init(SDL_INIT_VIDEO | SDL_INIT_JOYSTICK) < 0)
 	{
 		qDebug() << "Error initializing SDL:" << SDL_GetError();
+
 		return 0;
 	}
 
@@ -163,6 +191,7 @@ int main(int, char *argv[])
 	{
 		qDebug() << "Error initializing SDL_image:" << SDL_GetError();
 		SDL_Quit();
+
 		return 0;
 	}
 
@@ -171,6 +200,17 @@ int main(int, char *argv[])
 		qDebug() << "Error initializing SDL_ttf:" << SDL_GetError();
 		IMG_Quit();
 		SDL_Quit();
+
+		return 0;
+	}
+
+	if (Sound_Init() == 0)
+	{
+		qDebug() << "Error initializing SDL_sound:" << Sound_GetError();
+		TTF_Quit();
+		IMG_Quit();
+		SDL_Quit();
+
 		return 0;
 	}
 
@@ -241,6 +281,7 @@ int main(int, char *argv[])
 
 	SDL_DestroyWindow(win);
 
+	Sound_Quit();
 	TTF_Quit();
 	IMG_Quit();
 	SDL_Quit();