core: notify plugins when a log line is emitted.

Currently make a plugin that do reportings of logs on
a services like graphana is not possible. So this commit
include the possibility to write a plugin that do the report
of this analisys.

Changelog-Added: core: notify plugins when a log line is emitted.
Signed-off-by: Vincenzo Palazzo <vincenzopalazzodev@gmail.com>

common/plugin.c

@@ -0,0 +1,15 @@
+#include "config.h"
+#include <ccan/tal/str/str.h>
+#include <common/plugin.h>
+
+bool is_asterix_notification(const char *notification_name, const char *subscription)
+{
+	bool is_special;
+        /* Asterisk is magic "all", and log notification
+	 * is a special notification that must be turn on
+	 * only if requested. */
+	is_special = streq(subscription, "*") && !streq(notification_name, "log");
+	if (is_special)
+		return true;
+	return false;
+}