This picks up the case where the memberof attribute is an empty
array as well as not being an array

The OPENLDAP option uses hardcoded uid to search for. It should instead use the value of
attribute.username. This means it also changes the default since attribute.username
defaults to samAccountName. So update the docs to make the example work again. Has not
been in a release yet so should not break existing installations.

For #458

Added OpenLDAP case in getgroups function

(being respectful with occurences that might change the behaviour, i.e. default database prefixes)

This patch adds a common "base filter" for creating authproc filters
that access a LDAP directory, and it adds a filter
(ldap:AttributeAddUsersGroups) for adding group information.

Thanks to Ryan Panning for implementing this!

git-svn-id: https://simplesamlphp.googlecode.com/svn/trunk@2986 44740490-163a-0410-bde0-09ae8108e29a