s3-auth Add struct auth3_session_info to aid transition to auth_session info

s3-auth Add struct auth3_session_info to aid transition to auth_session info

This will allow a gradual conversion of the required elements from the
current struct auth_serversupplied_info.

This commit adds the structure definition and some helper functions to
copy between the two structures.

At this stage these structures and functions are IDENTICAL to the
existing code, and so show the past history of that code.  The plan is
to slowly modify them over the course of the patch series, so that the
changes being made a clear.

By using a seperate structure to auth_serversupplied_info we can
remove elements that are not needed after the authentication, and we
can choose a layout that best reflects the needs of runtime users,
rather than the internals of the authentication subsystem.

By eventually using the auth_session_info from auth.idl, we will gain
a single session authorization structure across the whole codebase,
allowing more code to be shared, and a much more transparent process
for forwarding authorization credentials over the named pipe proxy.

Andrew Bartlett

Signed-off-by: Andrew Tridgell <tridge@samba.org>