Try to enforce the use of a high performance NVIDIA / ATI GPU

on dual graphic card laptops.

xs/src/slic3r/GUI/GUI.cpp

@@ -5,6 +5,10 @@
 #elif _WIN32
 #include <Windows.h>
 #pragma comment(lib, "user32.lib")
+extern "C" {
+__declspec(dllexport) DWORD NvOptimusEnablement = 0x00000001;
+__declspec(dllexport) int AmdPowerXpressRequestHighPerformance = 1;
+}
 #endif
 
 namespace Slic3r { namespace GUI {