Merge remote-tracking branch 'asn/bug6788'

struct transport_t;

int find_transport_by_bridge_addrport(const tor_addr_t *addr, uint16_t port,

                                      const struct transport_t **transport);

const char *find_transport_name_by_bridge_addrport(const tor_addr_t *addr,

                                                   uint16_t port);

int validate_pluggable_transports_config(void);