I experienced troubles using libcurl with SSPI under Windows 9x
(particulary, Windows 98) and suggest patch to fix it.

First, Windows 9x don't have CompleteAuthToken() function, however
MSDN says it have. So I've implemented dynamic loading of this
function by GetProcAddress() and call it only if it's available. Tests
with MS ISA Server have shown that NTLM HTTP proxy authorization works
fine without this call under Windows 98.

Second, last parameter of AcquireCredentialsHandle() and
InitializeSecurityContext() (PTimeStamp ptsExpiry) seems to be
mandatory under Windows 9x, so I've added dummy variable:
TimeStamp tsDummy;
and pass pointer to it as last parameter in these calls.