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

cmd-line-utils/readline/bind.c

@@ -855,7 +855,7 @@ _rl_read_init_file (filename, include_level)
 {
   register int i;
   char *buffer, *openname, *line, *end;
-  size_t file_size;
+  size_t file_size = 0;
 
   current_readline_init_file = filename;
   current_readline_init_include_level = include_level;