Enable support of access to tables from triggers. Thus fix bug #8406 "Triggers

crash if referencing a table" and several other related bugs.
Fix for bug #11834 "Re-execution of prepared statement with dropped function
crashes server." which was spotted during work on previous bugs.

Also couple of nice cleanups:
- Replaced two separate hashes for stored routines used by statement with one.
- Now instead of doing one pass through all routines used in statement for
  caching them and then doing another pass for adding their tables to table
  list, we do only one pass during which do both things.

sql/sql_parse.cc

@@ -2296,8 +2296,7 @@ mysql_execute_command(THD *thd)
     Don't reset warnings when executing a stored routine.
   */
   if ((all_tables || &lex->select_lex != lex->all_selects_list ||
-       lex->spfuns.records || lex->spprocs.records) &&
-      !thd->spcont)
+       lex->sroutines.records) && !thd->spcont)
     mysql_reset_errors(thd, 0);
 
 #ifdef HAVE_REPLICATION