Merge separate RGSS version build configs into one

Setup active RGSS version at runtime. Desired version can be
specified via config, or as default, auto detected from the game
files. This removes the need to build specifically for each
version, which should help packaging a lot.

This also greatly reduces the danger of introducing code that
wouldn't compile on all RGSS version paths (as certain code paths
were completely ifdef'd out).

This can be optimized more, eg. not compiling shaders that aren't
needed in the active version.

src/shader.h

@@ -213,7 +213,6 @@ private:
 	GLint u_hueAdjust, u_inputTexture;
 };
 
-#ifdef RGSS2
 class SimpleMatrixShader : public ShaderBase
 {
 public:
@@ -255,8 +254,6 @@ private:
 	GLint u_aniOffset;
 };
 
-#endif
-
 /* Bitmap blit */
 class BltShader : public ShaderBase
 {
@@ -288,12 +285,9 @@ struct ShaderSet
 	SimpleTransShader simpleTrans;
 	HueShader hue;
 	BltShader blt;
-
-#ifdef RGSS2
 	SimpleMatrixShader simpleMatrix;
 	BlurShader blur;
 	TilemapVXShader tilemapVX;
-#endif
 };
 
 #endif // SHADER_H