libobs-d3d11: Do not allow Alt+Enter interception

Prevents Alt-Enter from attempting to automatically fullscreen an OBS
graphics display.

Closes obsproject/obs-studio#1248

libobs-d3d11/d3d11-subsystem.cpp

@@ -166,6 +166,9 @@ gs_swap_chain::gs_swap_chain(gs_device *device, const gs_init_data *data)
 	if (FAILED(hr))
 		throw HRError("Failed to create swap chain", hr);
 
+	/* Ignore Alt+Enter */
+	device->factory->MakeWindowAssociation(hwnd, DXGI_MWA_NO_ALT_ENTER);
+
 	Init();
 }