opengl32: Allocate WOW64 buffers struct with calloc. Avoid random crashes as vk_device isn't always zeroed. Fixes: ce5995cf099523cfb976b5a73f5871eb04f1a039.
opengl32: Set dummy context with wglMakeContextCurrentARB. wglMakeCurrent( NULL, NULL ) returns an early error if current context is already NULL.