BUILD: proto_tcp: export the correct names for proto_tcpv[46]

The exported names were not correct (missing the 'v').
diff --git a/include/haproxy/proto_tcp.h b/include/haproxy/proto_tcp.h
index 52566db..8a3d9fd 100644
--- a/include/haproxy/proto_tcp.h
+++ b/include/haproxy/proto_tcp.h
@@ -28,8 +28,8 @@
 #include <haproxy/listener-t.h>
 #include <haproxy/sample-t.h>
 
-extern struct protocol proto_tcp4;
-extern struct protocol proto_tcp6;
+extern struct protocol proto_tcpv4;
+extern struct protocol proto_tcpv6;
 
 int tcp_bind_socket(int fd, int flags, struct sockaddr_storage *local, struct sockaddr_storage *remote);
 int tcp_connect_server(struct connection *conn, int flags);