new lock for multiupdate:

- open and create derived tables
- detect which tables should be locked for write
- lock and fill derived tables
some unitialized variables fixed


mysql-test/r/lock_multi.result:
  correct results returned
mysql-test/r/multi_update.result:
  correct results returned
mysql-test/r/view.result:
  correct results returned
mysql-test/t/multi_update.test:
  correct results returned
mysql-test/t/view.test:
  correct results returned
sql/mysql_priv.h:
  derived tables processing splited on table creation and table filling
sql/sql_base.cc:
  derived tables processing splited on table creation and table filling
sql/sql_class.h:
  function to detect when we need fill derived tables
sql/sql_derived.cc:
  derived tables processing splited on table creation and table filling
sql/sql_lex.cc:
  fixed uninitialized value
sql/sql_load.cc:
  fixed uninitialized value
sql/sql_parse.cc:
  initialization muved (will be done for all queries)
sql/sql_prepare.cc:
  preparation of multiupdate changed a bit because new locking procedure
sql/sql_update.cc:
  new lock for multiupdate:
  - open and create derived tables
  - detect which tables should be locked for write
  - lock and fill derived tables
sql/table.h:
  place to store select_result between creation and filling tables

sql/sql_lex.cc

@@ -176,6 +176,7 @@ void lex_start(THD *thd, uchar *buf,uint length)
   lex->sphead= NULL;
   lex->spcont= NULL;
   lex->trg_table= NULL;
+  lex->proc_list.first= 0;
 
   extern byte *sp_lex_spfuns_key(const byte *ptr, uint *plen, my_bool first);
   hash_free(&lex->spfuns);