TRUNCATE TABLE fails to replicate when stmt-based binlogging is not supported.

There were two separate problems with the code, both of which are fixed with
this patch:

1. An error was printed by InnoDB for TRUNCATE TABLE in statement mode when
   the in isolation levels READ COMMITTED and READ UNCOMMITTED since InnoDB
   does permit statement-based replication for DML statements. However,
   the TRUNCATE TABLE is not transactional, but is a DDL, and should therefore
   be allowed to be replicated as a statement.

2. The statement was not logged in mixed mode because of the error above, but
   the error was not reported to the client.

This patch fixes the problem by treating TRUNCATE TABLE a DDL, that is, it is
always logged as a statement and not reporting an error from InnoDB for TRUNCATE
TABLE.


mysql-test/extra/binlog_tests/binlog_truncate.test:
  Adding new test to check that TRUNCATE TABLE is written correctly
  to the binary log.
mysql-test/extra/rpl_tests/rpl_truncate.test:
  Removing redundant testing by eliminating settings of BINLOG_FORMAT.
mysql-test/extra/rpl_tests/rpl_truncate_helper.test:
  Replacing slave and master reset code with include file.
  Removing settings of BINLOG_FORMAT.
  Replacing printing of table contents to compare master and slave
  with diff_tables.inc.
mysql-test/suite/binlog/t/binlog_truncate_innodb.test:
  Adding test for testing that TRUNCATE TABLE is logged correctly for InnoDB
  in all isolation levels.
mysql-test/suite/binlog/t/binlog_truncate_myisam.test:
  Adding test for testing that TRUNCATE TABLE is logged correctly for MyISAM.
mysql-test/suite/binlog/t/disabled.def:
  Disabling binlog_truncate_innodb since it does not work (yet).
sql/sql_base.cc:
  Correcting setting of capabilities flags to make the comparison with 0
  later in the code work correctly.
sql/sql_delete.cc:
  Re-organizing code to ensure that TRUNCATE TABLE is logged in statement
  format and that row format is not used unless there are rows to log (which
  there are not when delete_all_rows() is called, so this has to be logged
  as a statement).