WinPR SSPI Cleanup + Hardening

Implement basic Negotiate SSPI module (NTLM only)
Compile SSPI code on Windows, toggle dynamically between WinPR and Native implementation
Fix exporting of SSPI functions regardless of the Windows SSPI header definitions
Fix leaks and harden NTLM SSPI module
Add unit test for NTLM client+server authentication
Add support for querying User+Domain and setting NTLM hash