Update to latest version of freemarker (2.3.21)

See for discussion mailinglist: https://mail.google.com/mail/u/1/#label/Hippo-dev/14b26d952451c64d

The current version 7.9.5 (pom version 26) uses freemarker version 2.3.16.

If you want to use customer tag libraries, the .tld cannot be found in the site war project.

See:

• http://sourceforge.net/p/freemarker/bugs/338/

See Attila's comment (2011-05-09):
"""
Interestingly, I also realized that we never had the functionality for scanning for .tld files within WEB-INF directory tree, only for .tld files in .jar files in /WEB-INF/lib, so we were in violation of the spec there too.

"""
This is fixed in 2.3.17

2.3.18 also contains another JSTL TagLib related fix:

• http://sourceforge.net/p/freemarker/bugs/344/

Please update the Hippo MS pom to 2.3.21.