syslog: take the review notes on the state flag and the header length

The enabled flag is a flag, so say bool. The header length no longer needs
to live in xdata: it was put there when a local would not link, and there
is room for it here.

The overview names the row after the JSON key, so the syslog row said
"syslog_server_ip" while carrying only an address. It now says
"syslog_server" and carries the port with it.

syslog.c

@@ -12,11 +12,6 @@ __xdata char logbuf[LOGBUF_SIZE];
 __xdata struct syslog_state syslog_state;
 __xdata uip_ipaddr_t server_ip;
 
-/* Header length, in xdata rather than on the stack: syslog_callback() is
- * __banked, so a local here takes a byte of internal RAM nobody can overlay,
- * and the two it costs are enough to stop the image from linking. */
-__xdata uint16_t syslog_hdr;
-
 #define state syslog_state 
 
 void syslog_init(void) __banked
@@ -64,6 +59,7 @@ void syslog_stop(void) __banked
 
 void syslog_callback(uint16_t lport) __banked
 {
+	uint16_t syslog_hdr;
 	if (lport != state.syslog_conn->lport)
 		return;