Custom DllMain Windows

[Shucks]

@Yardanico I know but thats not I've asked for. The issue is that I need to 
pass the first argument (hinstDLL) from dllmain to my main function and AFAIK 
nim's default entry point doesn't spawns a thread for the main code. That 
causes issues in some cases because a injector for example waits for the return 
status of dllmain.