BUG#51291 Unfortunate effect around variable binlog_direct_non_transactional_updates

BUG#46364 introduced the flag binlog_direct_non_transactional_updates which
would make N-changes to be written to the binary log upon committing the
statement when "ON". On the other hand, when "OFF" the option was supposed
to mimic the behavior in 5.1. However, the implementation was not mimicking
the behavior correctly and the following bugs popped up:

  Case #1: N-changes executed within a transaction would go into
           the S-cache. When later in the same transaction a
           T-change occurs, N-changes following it were written
           to the T-cache instead of the S-cache. In some cases,
           this raises problems. For example, a
           Table_map_log_event being written initially into the
           S-cache, together with the initial N-changes, would be
           absent from the T-cache. This would log N-changes
           orphaned from a Table_map_log_event (thence discarded
           at the slave). (MIXED and ROW)

   Case #2: When rolling back a transaction, the N-changes that
            might be in the T-cache were disregarded and
            truncated along with the T-changes. (MIXED and ROW)

   Case #3: When a MIXED statement (TN) is ahead of any other
            T-changes in the transaction and it fails, it is kept
            in the T-cache until the transaction ends. This is
            not the case in 5.1 or Betony (5.5.2). In these, the
            failed TN statement would be written to the binlog at
            the same instant it had failed and not deferred until
            transaction end. (SBR)

To fix these problems, we have decided to do what follows:

   For Case #1 and #2, we circumvent them:

      1. by not letting binlog_direct_non_transactional_updates
         affect MIXED and RBR. These modes will keep the behavior
         provided by WL#2687. Although this will make Celosia to
         behave differently from 5.1, an execution will be always
         safe under such modes in the sense that slaves will never
         go out sync. In 5.1, using either MIXED or ROW while
         mixing N-statements and T-statements was not safe.

   For Case #3, we don't actually fix it. We:

      1. keep it and make all MIXED statements whether they end
         up failing or not or whether they are up front in the
         transaction or after some transactional change to always
         be stored in the T-cache. This means that it is written
         to the binary log on transaction commit/rollback only.

      2. We make the warning message even more specific about the
         MIXED statement and SBR.

mysql-test/suite/rpl/r/rpl_concurrency_error.result

@@ -22,7 +22,7 @@ SET AUTOCOMMIT = 1;
 BEGIN;
 UPDATE t SET f = 'yellow 2' WHERE i = 3;
 Warnings:
-Note	1592	Unsafe statement binlogged in statement format since BINLOG_FORMAT = STATEMENT. Reason for unsafeness: Non-transactional reads or writes are unsafe if they occur after transactional reads or writes inside a transaction.
+Note	1592	Unsafe statement binlogged in statement format since BINLOG_FORMAT = STATEMENT. Reason for unsafeness: Statements that read from both transactional and non-transactional tables and write to any of them are unsafe.
 SET AUTOCOMMIT = 1;
 BEGIN;
 UPDATE t SET f = 'magenta 2' WHERE f = 'red';
@@ -51,7 +51,7 @@ SET AUTOCOMMIT = 1;
 BEGIN;
 UPDATE t SET f = 'gray 2' WHERE i = 3;
 Warnings:
-Note	1592	Unsafe statement binlogged in statement format since BINLOG_FORMAT = STATEMENT. Reason for unsafeness: Non-transactional reads or writes are unsafe if they occur after transactional reads or writes inside a transaction.
+Note	1592	Unsafe statement binlogged in statement format since BINLOG_FORMAT = STATEMENT. Reason for unsafeness: Statements that read from both transactional and non-transactional tables and write to any of them are unsafe.
 SET AUTOCOMMIT = 1;
 BEGIN;
 UPDATE t SET f = 'dark blue 2' WHERE f = 'red';
@@ -77,7 +77,7 @@ master-bin.000001	#	Xid	#	#	COMMIT /* XID */
 SET AUTOCOMMIT = 0;
 UPDATE t SET f = 'yellow 1' WHERE i = 3;
 Warnings:
-Note	1592	Unsafe statement binlogged in statement format since BINLOG_FORMAT = STATEMENT. Reason for unsafeness: Non-transactional reads or writes are unsafe if they occur after transactional reads or writes inside a transaction.
+Note	1592	Unsafe statement binlogged in statement format since BINLOG_FORMAT = STATEMENT. Reason for unsafeness: Statements that read from both transactional and non-transactional tables and write to any of them are unsafe.
 SET AUTOCOMMIT = 0;
 UPDATE t SET f = 'magenta 1' WHERE f = 'red';
 ERROR HY000: Lock wait timeout exceeded; try restarting transaction
@@ -104,7 +104,7 @@ master-bin.000001	#	Query	#	#	ROLLBACK
 SET AUTOCOMMIT = 0;
 UPDATE t SET f = 'gray 1' WHERE i = 3;
 Warnings:
-Note	1592	Unsafe statement binlogged in statement format since BINLOG_FORMAT = STATEMENT. Reason for unsafeness: Non-transactional reads or writes are unsafe if they occur after transactional reads or writes inside a transaction.
+Note	1592	Unsafe statement binlogged in statement format since BINLOG_FORMAT = STATEMENT. Reason for unsafeness: Statements that read from both transactional and non-transactional tables and write to any of them are unsafe.
 SET AUTOCOMMIT = 0;
 UPDATE t SET f = 'dark blue 1' WHERE f = 'red';
 ERROR HY000: Lock wait timeout exceeded; try restarting transaction