BUG 13454045 - 63524: BUG #35396 "ABNORMAL/IMPOSSIBLE/LARGE QUERY_TIME AND LOCK_TIME" HAPPENS A

If a query's end time is before before its start time, the system clock has been turn back
(daylight savings time etc.). When the system clock is changed, we can't tell for certain a
given query was actually slow. We did not protect against logging such a query with a bogus
execution time (resulting from end_time - start_time being negative), and possibly logging it
even though it did not really take long to run.

We now have a sanity check in place.

sql/sql_parse.cc:
  Make sure end time is not before start time - otherwise, we can be SURE the system clock
  was changed in between, but not by how much. In other words, when the clock is changed,
  we don't know how long a query ran, and whether it was slow.

sql/sql_parse.cc

@@ -1734,8 +1734,9 @@ void log_slow_statement(THD *thd)
     ulonglong end_utime_of_query= thd->current_utime();
     thd_proc_info(thd, "logging slow query");
 
-    if (((end_utime_of_query - thd->utime_after_lock) >
-         thd->variables.long_query_time ||
+    if ((((end_utime_of_query > thd->utime_after_lock) &&
+          ((end_utime_of_query - thd->utime_after_lock) >
+           thd->variables.long_query_time)) ||
          ((thd->server_status &
            (SERVER_QUERY_NO_INDEX_USED | SERVER_QUERY_NO_GOOD_INDEX_USED)) &&
           opt_log_queries_not_using_indexes &&