IPv6: Improve address handling by Subnet (was 4639)

In some cases class Subnet handles converted IPv6 to IPv4 addresses in
an incorrect way: It accepts some invalid addresses and in some cases it
converts the address without adjusting the netmask.
This patch fixes these problems by adding special handling for special
addresses.

Acked-by: Tigran
Target: master
Require-book: no
Require-notes: no
gplazma-ldap: make DN search string configurable

added a new property to specify DN search criteria:

gplazma.ldap.userfilter

The default value is 'uid', which is used in posix
schema.

This is a very lite filter version. Can be changed if needed.

Acked-by: Paul Millar
Target: master,2.6
Require-book: yes
Require-notes: yes
Patch: http://rb.dcache.org/r/5922/