It's a regression issue.
The reason of the bug appeared to be an error introduced into 5.1 source code.
A piece of code in Create_file_log_event::do_apply_event() did not have test
coverage which made make test and pb unaware.
      
Fixed with inverting the old value of the return value from 
Create_file_log_event::do_apply_event().
The rpl test suite is extended with `rpl_cross_version' the file to hold 
regression cases similar to the current.

character_set_database !=character_set_server" is fixed.

This does not bring any contents changes, it is purely
metadata which are affected.

Details:

Even within 5.0, most of these changesets did not cause
file contents changes, because they were backports done
for the "service pack" builds of 5.0.66sp1 and 5.0.72sp1.

The "real" changesets are also already present in 5.1,
so this upmerge doesn't change any contents.

The only "real" changeset in 5.0 was a fix of the shell
scripts used to configure bdb (BerkeleyDB).
As we completele removed bdb from the 5.1 sources already,
the affected files are not present in the 5.1 source tree,
so this changeset also does not cause any contents changes.

this should not happen.

This is not the final merge of that release build, but we need early
access to these tool fixes (use of "awk" in the BDB configuration).

with mysql_change_user) to 5.0.

Post-fix test failure: fixed mysqlcheck.test on Windows platforms.

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.

The next number (AUTO_INCREMENT) field of the table for write
rows events are not initialized, and cause some engines (innodb)
not correctly update the tables's auto_increment value.

This patch fixed this problem by honor next number fields if present.

Use SELECT FROM INFORMATION_SCHEMA instead of SHOW VARIABLES LIKE to restrict
values correctly.

partition_innodb_semi_consistent.test, which was overlooked in the
innodb-5.1-ss3603 snapshot.

The problem is that the query cache stores packets containing
the server status of the time when the cached statement was run.
This might lead to a wrong transaction status in the client side
if a statement is cached during a transaction and is later served
outside a transaction context (and vice-versa).

The solution is to take into account the transaction status when
storing in and serving from the query cache.