logging_vty: Print 'log filter all' info in 'show logging vty'

When we print information about the current logging configuration,
it makes sense to also print information about the log filters.
diff --git a/src/vty/logging_vty.c b/src/vty/logging_vty.c
index ace346a..fc1ca43 100644
--- a/src/vty/logging_vty.c
+++ b/src/vty/logging_vty.c
@@ -247,6 +247,12 @@
  			info->cat[i].description,
 			VTY_NEWLINE);
 	}
+
+	vty_out(vty, " Log Filter 'ALL': %s%s",
+		tgt->filter_map & LOG_FILTER_ALL ? "Enabled" : "Disabled",
+		VTY_NEWLINE);
+
+	/* FIXME: print application specific filters */
 }
 
 #define SHOW_LOG_STR "Show current logging configuration\n"