QVulkanInstance destructor crash

Symptoms: Application crashes inside QVulkanInstance destructor if declared inside DLL

Steps to reproduce:

1. in main(), create QGuiApplication
2. in main(), call LoadLibrary(...) and get pointer to your function inside the DLL
3. call the function
4. inside your DLL, declare QVulkanInstance as global variable
5. inside your DLL's function, call QVulkanInstance::create()
6. call exit(0)

During application clean up, destructor of QVulkanInstance is called and it crashes the application.

Minimal example attached. MSVC 2015 (Update 3) was used. To compile example, update start.bat to set QTDIR to your Qt installation.