Remove sam/api.c.

Remove sam/api.c.

In order to reduce complexity, this patch removes the upper layer of the SAM
API.  Also, we remove the function pointers on the sam context - there really
is no point making these replaceable - that's for the modules.

Move a number of functions in include/interface.c around to allow for use of
'static' and to keep the external API in one chunk, at the bottem.  All these
functions were renamed to remove the context_sam -> sam

Consequential changes in the samtest module, and back out metze's change for
ACB filtering, becouse I think it belongs in the SAM backeds.  (But I will take
debate on this one).

Changes to the lib/util_sid.c code to create a 'system' token, and make it a
SAM_ASSERT() enforced requirement to have a token on those calls that specify
it.  samtest now uses this.

We should have a samtest call to set your own token.

We also need to extend our se_access code to cover the things that Win2k is
returning in it's access tokens.  Currently our system token doesn't pass, due
to unexpected flags.  (When running sam_ads against Win2k)

Andrew Bartlett