Fix for

bug#33094: Error in upgrading from 5.0 to 5.1 when table contains
triggers
and
#41385: Crash when attempting to repair a #mysql50# upgraded table
with triggers.

Problem:
1. trigger code didn't assume a table name may have
a "#mysql50#" prefix, that may lead to a failing ASSERT().
2. "ALTER DATABASE ... UPGRADE DATA DIRECTORY NAME" failed
for databases with "#mysql50#" prefix if any trigger.
3. mysqlcheck --fix-table-name didn't use UTF8 as a default
character set that resulted in (parsing) errors for tables with
non-latin symbols in their names and definitions of triggers.

Fix:
1. properly handle table/database names with "#mysql50#" prefix.
2. handle --default-character-set mysqlcheck option;
if mysqlcheck is launched with --fix-table-name or --fix-db-name
set default character set to UTF8 if no --default-character-set
option given.

Note: if given --fix-table-name or --fix-db-name option,
without --default-character-set mysqlcheck option
default character set is UTF8.


client/mysqlcheck.c:
  Fix for
  bug#33094: Error in upgrading from 5.0 to 5.1 when table contains
  triggers
  and
  #41385: Crash when attempting to repair a #mysql50# upgraded table
  with triggers.
    - check and set default charset if --default-character-set option
      given.
    - set default charset to "utf8" if there's
      --fix-table-name or --fix-db-name and no --default-character-set.
mysql-test/r/mysqlcheck.result:
  Fix for
  bug#33094: Error in upgrading from 5.0 to 5.1 when table contains
  triggers
  and
  #41385: Crash when attempting to repair a #mysql50# upgraded table
  with triggers.
    - test result.
mysql-test/t/mysqlcheck.test:
  Fix for
  bug#33094: Error in upgrading from 5.0 to 5.1 when table contains
  triggers
  and
  #41385: Crash when attempting to repair a #mysql50# upgraded table
  with triggers.
    - test case.
sql/mysql_priv.h:
  Fix for
  bug#33094: Error in upgrading from 5.0 to 5.1 when table contains
  triggers
  and
  #41385: Crash when attempting to repair a #mysql50# upgraded table
  with triggers.
    - check_n_cut_mysql50_prefix() introduced.
sql/sql_table.cc:
  Fix for
  bug#33094: Error in upgrading from 5.0 to 5.1 when table contains
  triggers
  and
  #41385: Crash when attempting to repair a #mysql50# upgraded table
  with triggers.
    - tablename_to_filename() code split into 2 parts
    - check_n_cut_mysql50_prefix() introduced to cut #mysql50# prefixes,
      used in the trigger code as well.
sql/sql_trigger.cc:
  Fix for
  bug#33094: Error in upgrading from 5.0 to 5.1 when table contains
  triggers
  and
  #41385: Crash when attempting to repair a #mysql50# upgraded table
  with triggers.
    - Table_triggers_list::check_n_load() - checking triggers assume
      a table/database name given may have "#mysql50#" prefix in some cases.
    - Table_triggers_list::change_table_name_in_triggers() -
      create .TRG file in new database directory and delete it in old one,
      as they may differ in case of
      "ALTER DATABASE ... UPGRADE DATA DIRECTORY NAME"
    - Table_triggers_list::change_table_name_in_trignames() - remove stale .TRN
      files in #mysql50#dbname directory in case of database upgrade
    - Table_triggers_list::change_table_name() - allow changing trigger's
      database in case of its upgrading
sql/sql_trigger.h:
  Fix for
  bug#33094: Error in upgrading from 5.0 to 5.1 when table contains
  triggers
  and
  #41385: Crash when attempting to repair a #mysql50# upgraded table
  with triggers.
    - new old_db_name parameter added in
      Table_triggers_list::change_table_name_in_trignames() and
      Table_triggers_list::change_table_name_in_triggers()

sql/sql_trigger.h

@@ -146,11 +146,13 @@ public:
 
 private:
   bool prepare_record1_accessors(TABLE *table);
-  LEX_STRING* change_table_name_in_trignames(const char *db_name,
+  LEX_STRING* change_table_name_in_trignames(const char *old_db_name,
+                                             const char *new_db_name,
                                              LEX_STRING *new_table_name,
                                              LEX_STRING *stopper);
   bool change_table_name_in_triggers(THD *thd,
-                                     const char *db_name,
+                                     const char *old_db_name,
+                                     const char *new_db_name,
                                      LEX_STRING *old_table_name,
                                      LEX_STRING *new_table_name);
 };