[ENH] More documentation strings in lib/userslib.php

git-svn-id: file:///var/local/code.tiki.org/tikisvn/branches/12.x@51999 b456876b-0849-0410-b77d-98878d47e9d5
[REVERT] Revert r51999 More documentation strings in lib/userslib.php

git-svn-id: file:///var/local/code.tiki.org/tikisvn/branches/12.x@52000 b456876b-0849-0410-b77d-98878d47e9d5