Merge with MySQL 5.1.55

- Fixed some issues with partitions and connection_string, which also fixed lp:716890 "Pre- and post-recovery crash in Aria"
- Fixed wrong assert in Aria

Now need to merge with latest xtradb before pushing 

sql/ha_partition.cc:
  Ensure that m_ordered_rec_buffer is not freed before close.
sql/mysqld.cc:
  Changed to use opt_stack_trace instead of opt_pstack.
  Removed references to pstack
sql/partition_element.h:
  Ensure that connect_string is initialized
storage/maria/ma_key_recover.c:
  Fixed wrong assert

sql/sql_binlog.cc

@@ -50,6 +50,13 @@ void mysql_client_binlog_statement(THD* thd)
   }
   size_t decoded_len= base64_needed_decoded_length(coded_len);
 
+  /*
+    thd->options will be changed when applying the event. But we don't expect
+    it be changed permanently after BINLOG statement, so backup it first.
+    It will be restored at the end of this function.
+  */
+  ulonglong thd_options= thd->options;
+
   /*
     Allocation
   */
@@ -236,6 +243,7 @@ void mysql_client_binlog_statement(THD* thd)
   my_ok(thd);
 
 end:
+  thd->options= thd_options;
   rli->clear_tables_to_lock();
   my_free(buf, MYF(MY_ALLOW_ZERO_PTR));
   DBUG_VOID_RETURN;