Add support for GLSL 4.30 and GLSL ES 3.10, via #pragma language glsl4.

macOS and iOS won't support glsl4 until a Metal backend is implemented.

--HG--
branch : minor

src/modules/graphics/Graphics.h

@@ -163,6 +163,7 @@ public:
 		FEATURE_PIXEL_SHADER_HIGHP,
 		FEATURE_SHADER_DERIVATIVES,
 		FEATURE_GLSL3,
+		FEATURE_GLSL4,
 		FEATURE_INSTANCING,
 		FEATURE_MAX_ENUM
 	};