Bug #27119 server crash with integer division by zero during filesort on huge result

Fixed a problem and compiler warning on 64bit platforms so that they only allocated UINT_MAX number of BUFFPEKS.

sql/filesort.cc

@@ -370,7 +370,7 @@ static BUFFPEK *read_buffpek_from_file(IO_CACHE *buffpek_pointers, uint count)
   ulong length;
   BUFFPEK *tmp;
   DBUG_ENTER("read_buffpek_from_file");
-  if ((ulong)count > ULONG_MAX/sizeof(BUFFPEK))
+  if (count > UINT_MAX/sizeof(BUFFPEK))
     return 0; /* sizeof(BUFFPEK)*count will overflow */
   tmp=(BUFFPEK*) my_malloc(length=sizeof(BUFFPEK)*count, MYF(MY_WME));
   if (tmp)
@@ -604,7 +604,7 @@ write_keys(SORTPARAM *param, register uchar **sort_keys, uint count,
                        MYF(MY_WME)))
     goto err;                                   /* purecov: inspected */
   /* check we won't have more buffpeks than we can possibly keep in memory */
-  if (my_b_tell(buffpek_pointers) + sizeof(BUFFPEK) > (ulonglong)ULONG_MAX)
+  if (my_b_tell(buffpek_pointers) + sizeof(BUFFPEK) > (ulonglong)UINT_MAX)
     goto err;
   buffpek.file_pos= my_b_tell(tempfile);
   if ((ha_rows) count > param->max_rows)