Cast pointers to uintptr_t rather than unsigned int.

Avoids potential warnings on PPC64 systems.

libswscale/ppc/swscale_altivec_template.c

@@ -29,13 +29,13 @@ altivec_packIntArrayToCharArray(int *val, uint8_t* dest, int dstW)
     register int i;
     vector unsigned int altivec_vectorShiftInt19 =
         vec_add(vec_splat_u32(10), vec_splat_u32(9));
-    if ((unsigned int)dest % 16) {
+    if ((uintptr_t)dest % 16) {
         /* badly aligned store, we force store alignment */
         /* and will handle load misalignment on val w/ vec_perm */
         vector unsigned char perm1;
         vector signed int v1;
         for (i = 0 ; (i < dstW) &&
-            (((unsigned int)dest + i) % 16) ; i++) {
+            (((uintptr_t)dest + i) % 16) ; i++) {
                 int t = val[i] >> 19;
                 dest[i] = (t < 0) ? 0 : ((t > 255) ? 255 : t);
         }