Correct spelling mistakes.

code/renderergl2/tr_bsp.c

@@ -1947,7 +1947,7 @@ static	void R_LoadNodesAndLeafs (lump_t *nodeLump, lump_t *leafLump) {
 		out->nummarksurfaces = LittleLong(inLeaf->numLeafSurfaces);
 	}	
 
-	// chain decendants
+	// chain descendants
 	R_SetParent (s_worldData.nodes, NULL);
 }