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.h

@@ -1,6 +1,7 @@
 #ifndef _SYSLOG_H_
 #define _SYSLOG_H_
 
+#include <stdbool.h>
 #include <stdint.h>
 
 #define LOGBUF_SIZE 512
@@ -8,7 +9,7 @@
 #define SYSLOG_PORT_DEFAULT 514
 
 struct syslog_state {
-    uint8_t enabled;
+    bool enabled;
     uint8_t line_available;
     uint16_t writeptr ;
     uint16_t readptr;