Added some casts for 32-bit machines

When both 'int' and 'l_obj' have 32 bits, an unsigned int needs a
cast to be assigned to 'l_obj'. (As long as 'l_obj' can count the
total memory used by the system, these casts should be safe.)

lobject.c

@@ -87,7 +87,7 @@ lu_byte luaO_codeparam (unsigned int p) {
 ** overflow, so we check which order is best.
 */
 l_mem luaO_applyparam (lu_byte p, l_mem x) {
-  unsigned int m = p & 0xF;  /* mantissa */
+  int m = p & 0xF;  /* mantissa */
   int e = (p >> 4);  /* exponent */
   if (e > 0) {  /* normalized? */
     e--;  /* correct exponent */