TAGS: reformat to fix when PRINTF_FMT() used.

I was wondering why TAGS was missing some functions, and finally
tracked it down: PRINTF_FMT() confuses etags if it's at the start
of a function, and it ignores the rest of the file.

So we put PRINTF_FMT at the end, but that doesn't work for
*definitions*, only *declarations*.  So we remove it from definitions
and add gratuitous declarations in the few static places.1

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

ccan/ccan/json_out/json_out.h

@@ -87,11 +87,11 @@ bool json_out_end(struct json_out *jout, char type);
  * If the resulting string requires escaping, and @quote is true, we
  * call json_escape().
  */
-PRINTF_FMT(4,5)
 bool json_out_add(struct json_out *jout,
 		  const char *fieldname,
 		  bool quote,
-		  const char *fmt, ...);
+		  const char *fmt, ...)
+	PRINTF_FMT(4,5);
 
 /**
  * json_out_addv - add a formatted member (vararg variant)