BSD socket SO_REUSEADDR is not a complete match, but features like
"allow binding to a port immediately after closing it" seem to be compatible.

For now, those pointers are always null, anyway.

This patch initializes allocated pointers in PointerUnmarshall since later
code checks the value for NULL (specifically, NdrConformantArrayUnmarshall).

This initializes the memory for an [in] parameter.

include: Take care to not declare CtxtHandle and PCtxtHandle more than once when including both sspi.h and wincred.h.