Change the internal constant color from a (per-draw) vertex attribute to a uniform. Pack most built-in uniforms into a single vec4 array and update them all with a single glUniform call.

--HG--
branch : minor

src/modules/graphics/vertex.h

@@ -43,7 +43,6 @@ enum BuiltinVertexAttribute
 	ATTRIB_POS = 0,
 	ATTRIB_TEXCOORD,
 	ATTRIB_COLOR,
-	ATTRIB_CONSTANTCOLOR,
 	ATTRIB_MAX_ENUM
 };
 
@@ -52,7 +51,6 @@ enum BuiltinVertexAttributeFlag
 	ATTRIBFLAG_POS = 1 << ATTRIB_POS,
 	ATTRIBFLAG_TEXCOORD = 1 << ATTRIB_TEXCOORD,
 	ATTRIBFLAG_COLOR = 1 << ATTRIB_COLOR,
-	ATTRIBFLAG_CONSTANTCOLOR = 1 << ATTRIB_CONSTANTCOLOR
 };
 
 enum BufferType