Drupal 6.33
Merge tag '6.33'

6.33 release
Merge pull request #91 from pressflow/merge-6.33

Merge 6.33 for SA-CORE-2014-004
Merge remote-tracking branch 'upstream/master'
README.md: add upgrade instructions

Signed-off-by: Paul Campbell <paulcampbell@fife.ac.uk>