s4:dsdb/common: dsdb_trust_normalize_forest_info_step[1,2]() and dsdb_trust_verify_fo...

s4:dsdb/common: dsdb_trust_normalize_forest_info_step[1,2]() and dsdb_trust_verify_forest_info()

These will be used in dcesrv_lsa_lsaRSetForestTrustInformation() in the
following order:

- dsdb_trust_normalize_forest_info_step1() verifies the input
  forest_trust_information and does some basic normalization.

- the output of step1 is used in dsdb_trust_verify_forest_info()
  to verify overall view of trusts and forests, this may generate
  collision records and marks records as conflicting.

- dsdb_trust_normalize_forest_info_step2() prepares the records
  to be stored in the msDS-TrustForestTrustInfo attribute.

Signed-off-by: Stefan Metzmacher <metze@samba.org>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>