Replace LoadIcon with LoadImage

Fixes #585.

src/win32_window.c

@@ -715,11 +715,15 @@ GLFWbool _glfwRegisterWindowClass(void)
     wc.lpszClassName = _GLFW_WNDCLASSNAME;
 
     // Load user-provided icon if available
-    wc.hIcon = LoadIconW(GetModuleHandleW(NULL), L"GLFW_ICON");
+    wc.hIcon = LoadImageW(GetModuleHandleW(NULL),
+                          L"GLFW_ICON", IMAGE_ICON,
+                          0, 0, LR_DEFAULTSIZE | LR_SHARED);
     if (!wc.hIcon)
     {
         // No user-provided icon found, load default icon
-        wc.hIcon = LoadIconW(NULL, IDI_WINLOGO);
+        wc.hIcon = LoadImageW(NULL,
+                              IDI_APPLICATION, IMAGE_ICON,
+                              0, 0, LR_DEFAULTSIZE | LR_SHARED);
     }
 
     if (!RegisterClassW(&wc))