[MOD] Use a shorter pre-/suffix for user preferences. The key field length is 40 chars 

git-svn-id: file:///var/local/code.tiki.org/tikisvn/trunk@49548 b456876b-0849-0410-b77d-98878d47e9d5
[FIX] Check mcrypt installation status when enabling the User Encryption feature

git-svn-id: file:///var/local/code.tiki.org/tikisvn/trunk@49549 b456876b-0849-0410-b77d-98878d47e9d5