Otherwise, the call will now fail with SEC_E_INVALID_HANDLE.

secur32: Fix NTLM's InitializeSecurityContextA/W to be flexible with the index of the token buffer in both the input and output buffer descriptions.

secur32: Make the NTLM SSP cope with a NULL phCredential parameter when InitializeSecurityContext is called more than once.

secur32: Fix the wrapper InitializeSecurityContextA/W functions to handle phContext and phNewContext parameters being optional for some SSPs.

oleaut32: SLTG references are only unique at the typeinfo level, so convert them to be unique to the typelib.

Unify write_pointers with write_embedded_types, and handle pointers in
unions.  Includes tests.