Implementation and stability patches

This pull request contains:
 - Implementation for RopModifyRecipients request with partian x500dn
 - fixed use-after-free in EcDoRpcExt2 function
 - this commit allow for uses like:
   openchange_newuser --create --enable 'kcurtis'
 - check for return value for emsmdbp_object_open_folder_by_fid() in EcDoRpc_RopSyncImportHierarchyChange()
I think this patch already went in some time ago. I will rebase the pull request to see what's left.
other that that, you are right 0 and 2 is not very descriptive (I don't know what they mean, but I will check).

thanks!