sql/item.cc:
  Code cleanup
sql/item.h:
  Code cleanup
sql/log.cc:
  Added comments
sql/sp_head.cc:
  Code cleanup patch from Monty: 
  in subst_spvars()
  - Move local variables first in block
  - Use res|= instead of res |=
  - Use strmake() instead of alloc + memcpy
  Added:
  - Fail the query if we don't have enough memory to produce a binlog-suitable query string: 
    if we're so low on memory we're likely to fail the query anyway, and failing now removes
    the need for hack with THD::query_str_binlog_suitable.
sql/sql_class.cc:
  Remove THD::query_str_binlog_unsuitable
sql/sql_class.h:
  Remove THD::query_str_binlog_unsuitable
sql/sql_delete.cc:
  Remove THD::query_str_binlog_unsuitable
sql/sql_insert.cc:
  Remove THD::query_str_binlog_unsuitable
sql/sql_parse.cc:
  Code cleanup
sql/sql_update.cc:
  Remove THD::query_str_binlog_unsuitable