Revert "Remove use of volatile in stored_field_cmp_to_item"

This reverts commit 7603463. The commit itself is fine, however when disabling volatile, compiler optimizations mess up our double results due to precision differences. Revert the patch till a proper solution is found.

Author: cvicentiu

sql/item.cc

@@ -8924,10 +8924,15 @@ int stored_field_cmp_to_item(THD *thd, Field *field, Item *item)
  }
  return my_time_compare(&field_time, &item_time);
  }
- double result= item->val_real();
+ /*
+ The patch for Bug#13463415 started using this function for comparing
+ BIGINTs. That uncovered a bug in Visual Studio 32bit optimized mode.
+ Prefixing the auto variables with volatile fixes the problem....
+ */
+ volatile double result= item->val_real();
  if (item->null_value)
  return 0;
- double field_result= field->val_real();
+ volatile double field_result= field->val_real();
  if (field_result < result)
  return -1;
  else if (field_result > result)