+ * Use: Main message token formatting driver. The arguments are
+ * interleaved formatting tokens and their parameters, finally
+ * terminated by an entry @A_END@.
+ *
+ * Tokens recognized:
+ *
+ * * "*..." ... -- pretokenized @dstr_putf@-like string
+ *
+ * * "?ADDR" SOCKADDR -- a socket address, to be converted
+ *
+ * * "?B64" BUFFER SIZE -- binary data to be base64-encoded
+ *
+ * * "?TOKENS" VECTOR -- null-terminated vector of tokens
+ *
+ * * "?PEER" PEER -- peer's name
+ *
+ * * "?ERRNO" ERRNO -- system error code
+ *
+ * * "[!]..." ... -- @dstr_putf@-like string as single token