Win32: Fix GLFW_MAXIMIZED ignored by first window

Fixes #780.

src/win32_init.c

@@ -319,6 +319,10 @@ static HWND createHelperWindow(void)
         return NULL;
     }
 
+    // HACK: The first call to ShowWindow is ignored if the parent process
+    //       passed along a STARTUPINFO, so clear that flag with a no-op call
+    ShowWindow(window, SW_HIDE);
+
     // Register for HID device notifications
     {
         DEV_BROADCAST_DEVICEINTERFACE_W dbi;