Fix warnings and remove casts by adding copy_vx_vx_uchar() functions.

source/blender/blenloader/intern/versioning_260.c

@@ -343,7 +343,7 @@ static void do_versions_mesh_mloopcol_swap_2_62_1(Mesh *me)
 		if (layer->type == CD_MLOOPCOL) {
 			mloopcol = (MLoopCol *)layer->data;
 			for (i = 0; i < me->totloop; i++, mloopcol++) {
-				SWAP(char, mloopcol->r, mloopcol->b);
+				SWAP(unsigned char, mloopcol->r, mloopcol->b);
 			}
 		}
 	}