Log Message:
Changes 5.5.21:
* A new CMake option, MYSQL_PROJECT_NAME, can be set on Windows or Mac OS X to
  be used in the project name.
Bugs Fixed
* Performance: InnoDB Storage Engine: Memory allocation for InnoDB tables was
  reorganized to reduce the memory overhead for large numbers of tables or
  partitions, avoiding situations where the “resident set size” could grow
  regardless of FLUSH TABLES statements. The problem was most evident for tables
  with large row size.
* Incompatible Change: An earlier change (in MySQL 5.1.62 and 5.5.21) was found
  to modify date-handling behavior in General Availability-status series (MySQL
  5.1 and 5.5). This change has been reverted.
* The change was that several functions became more strict when passed a DATE()
  function value as their argument, thus they rejected incomplete dates with
  a day part of zero. These functions were affected: CONVERT_TZ(), DATE_ADD(),
  DATE_SUB(), DAYOFYEAR(), LAST_DAY(), TIMESTAMPDIFF(), TO_DAYS(), TO_SECONDS(),
  WEEK(), WEEKDAY(), WEEKOFYEAR(), YEARWEEK(). The previous behavior has been
  restored.
* InnoDB Storage Engine: A Valgrind error was fixed in the function
  os_aio_init().
* InnoDB Storage Engine: The server could crash when creating an InnoDB
  temporary table under Linux, if the $TMPDIR setting points to a tmpfs
  filesystem and innodb_use_native_aio is enabled, as it is by default in MySQL
  5.5.4 and higher.
* InnoDB Storage Engine: References to C preprocessor symbols and macros
  HAVE_purify, UNIV_INIT_MEM_TO_ZERO, and UNIV_SET_MEM_TO_ZERO were removed
  from the InnoDB source code. They were only used in debug builds instrumented
  for Valgrind. They are replaced by calls to the UNIV_MEM_INVALID() macro.