OpenGL2: Remove map color scaling and r_forceSunMapLightScale.

Also simplify overbright code in ComputeShaderColors().

code/renderergl2/tr_shader.c

@@ -1826,11 +1826,13 @@ static qboolean ParseShader( char **text )
 
 			if (isGL2Sun)
 			{
-				token = COM_ParseExt( text, qfalse );
-				tr.mapLightScale = atof(token);
-
 				token = COM_ParseExt( text, qfalse );
 				tr.sunShadowScale = atof(token);
+
+				// parse twice, since older shaders may include mapLightScale before sunShadowScale
+				token = COM_ParseExt( text, qfalse );
+				if (token[0])
+					tr.sunShadowScale = atof(token);
 			}
 
 			SkipRestOfLine( text );