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>

lightningd/log.c

@@ -140,7 +140,7 @@ struct log_book *new_log_book(struct lightningd *ld, size_t max_mem,
 }
 
 /* With different entry points */
-struct log *PRINTF_FMT(3,4)
+struct log *
 new_log(const tal_t *ctx, struct log_book *record, const char *fmt, ...)
 {
 	struct log *log = tal(ctx, struct log);