Mega patch against nss_ldap 264

I have just pushed a large patch against nss_Ldap 264 up to the bugzilla.

This is a structural alteration at the source code level to ldap-nss.c
which is generally just changing how it reads. However, it fixes some
bugs in the kerberos pathways and also commons up code that had multiple
copies in the code source.

I would be very grateful if anybody could try it out and let me know
what I have broken.

My intention with this is to make the critical path through the code run
the minimal code when a connection to the LDAP server exists, make
recovery on failure more resilient, and provide for multiple SASL mechs
without need to alter the ldap-nss code.

Comments, improvements and fault reports much appreciated.

I am hoping that Luke will push this out as the basis for the main
development downstream, so that I can add the extra features on the
kerberos side I am looking for.

Howard.