pdb server: allow carrier id 0

(cherry-picked from commit 60ded00a3b574a08457a696334d11d668595cc0b)

utils/pdbt/common.h

@@ -32,7 +32,7 @@
  -1000..-1 used in dtm to indicate a carrier id and that no more nodes will follow (leaf node compression).
  -1001 used in dtm to mark a pointer to a child node as NULL.
 */
-#define MIN_PDB_CARRIERID 1
+#define MIN_PDB_CARRIERID 0
 #define MAX_PDB_CARRIERID 999
 #define OTHER_CARRIERID 1000
 #define MAX_CARRIERID 1000