split some security related functions in their own files.

split some security related functions in their own files.
(no need to include all of smbd files to use some basic sec functions)

also minor compile fixes
couldn't compile to test these due to some kerberos problems wirh 3.0,
but on HEAD they're working well, so I suppose it's ok to commit
(This used to be commit c78f2d0bd15ecd2ba643bb141cc35a3405787aa1)