WL#4967: Apply Google IO rate patch to Server

Affects: Server-5.4   —   Status: Complete   —   Priority: Medium

MySQL 5.4.0:
To improve the InnoDB I/O subsystem's ability to make more effective 
use of available I/O capacity, apply the Google IO rate patch from the 
launchpad tree 5.1-patches maintained by Mark Callaghan:
http://code.google.com/p/google-mysql-tools/wiki/InnodbIoTuning
Applied to MySQL 5.4.0.

Community contribution; for details, follow the link to launchpad:
http://code.google.com/p/google-mysql-tools/wiki/InnodbIoTuning
and the MySQL 5.4.0 description:
http://dev.mysql.com/doc/mysql-5.4-features/en/innodb-io-changes.html

Patch adds:
* innodb_io_capacity - number of disk IOPs the server can do. Rate 
limiting is used to prevent IO done by background threads from using 
all of the capacity of the server. 
* innodb_extra_dirty_writes - flush dirty buffer pages when dirty pct 
is less than max dirty pct 
Community contribution; no further LLD needed.