* Don't activate prelocking mode for evaluating procedure arguments when it is not necessary.
* Code structure simplification and cleanup.
* Cleanup in .test files


mysql-test/r/sp-prelocking.result:
  Prelocking-free SPs, post-review fixes:
  Added comment, s/testdb/mysqltest/, fixed a wrong test (error wasnt reported because of known bug in mysqltestrun)
mysql-test/r/sp-security.result:
  Don't drop the table we're not using.
mysql-test/r/sp.result:
  Prelocking-free SPs, post-review fixes:
  remove redundant "drop table if exists t3" statements
mysql-test/t/sp-prelocking.test:
  Prelocking-free SPs, post-review fixes:
  Added comment, s/testdb/mysqltest/, fixed a wrong test (error wasnt reported because of known bug in mysqltestrun)
mysql-test/t/sp-security.test:
  Don't drop the table we're not using.
mysql-test/t/sp.test:
  Prelocking-free SPs, post-review fixes:
  remove redundant "drop table if exists t3" statements
sql/sp.cc:
  New, better defined, sp_get_prelocking_info() function to get info about
    statement prelocking options
sql/sp.h:
  Prelocking-free SPs, post-review fixes: New, better defined, sp_get_prelocking_info() 
  function to get info about statement prelocking options
sql/sp_cache.h:
  Prelocking-free SPs, post-review fixes: Amended the comments
sql/sp_head.cc:
  Prelocking-free SPs, post-review fixes: Amend the comments, simplify the code that 
  attaches removes statement's prelocking tables.
sql/sql_base.cc:
  Prelocking-free SPs, post-review fixes:
  * Use a better defined sp_get_prelocking_info() function to get info about 
    statement prelocking options
  * Don't activate prelocked mode for evaluation of SP arguments that use tables 
    but don't need prelocking.
sql/sql_class.cc:
  Prelocking-free SPs, post-review fixes: Initialize THD members in the order they are declared.