Include v3 in documented 'protocols' in rend_service_descriptor_t

Also make it unsigned and document that it's for INTRODUCE cell versions.

Fixes 9099; bugfix on 0.2.1.5-alpha, which introduced the v3 protocol.

changes/bug9099

@@ -0,0 +1,5 @@
+  o Minor bugfixes:
+    - Fix a comment about the rend_server_descriptor_t.protocols field
+      to more accurately describe its range. Also, make that
+      field unsigned, to more accurately reflect its usage.
+      Fixes bug 9099; bugfix on 0.2.1.5-alpha.

src/or/or.h

@@ -4838,9 +4838,9 @@ typedef struct rend_service_descriptor_t {
   crypto_pk_t *pk; /**< This service's public key. */
   int version; /**< Version of the descriptor format: 0 or 2. */
   time_t timestamp; /**< Time when the descriptor was generated. */
-  /** Bitmask: which rendezvous protocols are supported?
-   * (We allow bits '0', '1', and '2' to be set.) */
-  int protocols : REND_PROTOCOL_VERSION_BITMASK_WIDTH;
+  /** Bitmask: which introduce/rendezvous protocols are supported?
+   * (We allow bits '0', '1', '2' and '3' to be set.) */
+  unsigned protocols : REND_PROTOCOL_VERSION_BITMASK_WIDTH;
   /** List of the service's introduction points.  Elements are removed if
    * introduction attempts fail. */
   smartlist_t *intro_nodes;