added a basic dcerpc endpoint mapper to Samba4. Currently only

implements the epm_Lookup() call, I'll add the other important calls
soon. I was rather pleased to find that epm_Lookup() worked first
time, which is particularly surprising given its complexity.

This required quite a bit of new infrastructure:

  * a generic way of handling dcerpc policy handles in the rpc server

  * added type checked varients of talloc. These are much less error
    prone. I'd like to move to using these for nearly all uses of
    talloc.

  * added more dcerpc fault handling code, and translation from
    NTSTATUS to a dcerpc fault code

  * added data_blob_talloc_zero() for allocating an initially zero
    blob

  * added a endpoint enumeration hook in the dcerpc endpoint server
    operations

source/lib/data_blob.c

@@ -87,6 +87,18 @@ DATA_BLOB data_blob_talloc(TALLOC_CTX *mem_ctx, const void *p, size_t length)
 	return ret;
 }
 
+/*******************************************************************
+ construct a zero data blob, using supplied TALLOC_CTX. 
+ use this sparingly as it initialises data - better to initialise
+ yourself if you want specific data in the blob
+*******************************************************************/
+DATA_BLOB data_blob_talloc_zero(TALLOC_CTX *mem_ctx, size_t length)
+{
+	DATA_BLOB blob = data_blob_talloc(mem_ctx, NULL, length);
+	data_blob_clear(&blob);
+	return blob;
+}
+
 /*******************************************************************
 free a data blob
 *******************************************************************/