samba - Apr 2015 - required settings to allow XP clients to access samba 4.2 servers

Dear list, 

the release notes of Samba 4.2.0 have one paragraph discussing 
some changes implemented to increase security - apparently these 
changes seem to break the access of XP clients unless some of the 
new features are disabled. 

That's perfectly fine - however: can someone briefly point out, 
which options need to be set on the AD DC and which ones on a 
member server. Many thanks for that - I have to admit, that I 
don't have the background to derive this from the release notes. :-( 

Thank You in advance! And best regards
Peter