Add -B scripts flag to allow debug output of script load order.

This patch adds a "scripts" option to -B, when Bro is enabled with
--enable-debug. This option will output information about the scripts
that are loaded to debug.log, showing their exact load order.

src/DebugLogger.h

@@ -33,6 +33,7 @@ enum DebugStream {
 	DBG_BROXYGEN,	// Broxygen
 	DBG_PKTIO,	// Packet sources and dumpers.
 	DBG_BROKER,	// Broker communication
+	DBG_SCRIPTS,	// Script initialization
 
 	NUM_DBGS // Has to be last
 };