NTLM single-sign on adjustments (XI)

Feature string literal NTLM_SSO renamed to NTLM_WB.
Preprocessor symbol USE_NTLM_SSO renamed to WINBIND_NTLM_AUTH_ENABLED.
curl's 'long' option 'ntlm-sso' renamed to 'ntlm-wb'.
Fix some comments to make clear that this is actually a NTLM delegation.