[net processing] Message handling for getcfcheckpt.

If -peerblockfilters is configured, handle requests for cfcheckpt.

src/protocol.cpp

@@ -40,6 +40,8 @@ const char *SENDCMPCT="sendcmpct";
 const char *CMPCTBLOCK="cmpctblock";
 const char *GETBLOCKTXN="getblocktxn";
 const char *BLOCKTXN="blocktxn";
+const char *GETCFCHECKPT="getcfcheckpt";
+const char *CFCHECKPT="cfcheckpt";
 } // namespace NetMsgType
 
 /** All known message types. Keep this in the same order as the list of
@@ -71,6 +73,8 @@ const static std::string allNetMessageTypes[] = {
     NetMsgType::CMPCTBLOCK,
     NetMsgType::GETBLOCKTXN,
     NetMsgType::BLOCKTXN,
+    NetMsgType::GETCFCHECKPT,
+    NetMsgType::CFCHECKPT,
 };
 const static std::vector<std::string> allNetMessageTypesVec(allNetMessageTypes, allNetMessageTypes+ARRAYLEN(allNetMessageTypes));