initialize some uninitialized variables.

really just nitpicking (keep valgrind clean).

gtk2_ardour/editor.cc

@@ -380,6 +380,7 @@ Editor::Editor ()
 	region_edit_menu_split_item = 0;
 	temp_location = 0;
 	leftmost_frame = 0;
+	mouse_mode = MouseObject;
 	current_stepping_trackview = 0;
 	entered_track = 0;
 	entered_regionview = 0;

gtk2_ardour/engine_dialog.cc

@@ -100,6 +100,7 @@ EngineControl::EngineControl ()
 	, _desired_sample_rate (0)
 	, started_at_least_once (false)
 	, queue_device_changed (false)
+	, _have_control (true)
 	, block_signals(0)
 {
 	using namespace Notebook_Helpers;