Allow drawing sun in OpenGL1 renderer

Removed #if 0 ... #endif around RB_DrawSun().
Merged improvements and changes from OpenGL2 renderer.

code/renderergl1/tr_backend.c

@@ -668,9 +668,10 @@ void RB_RenderDrawSurfList( drawSurf_t *drawSurfs, int numDrawSurfs ) {
 		qglDepthRange (0, 1);
 	}
 
-#if 0
-	RB_DrawSun();
-#endif
+	if (r_drawSun->integer) {
+		RB_DrawSun(0.1, tr.sunShader);
+	}
+
 	// darken down any stencil shadows
 	RB_ShadowFinish();