Cygwin: seteuid: use Kerberos/MsV1_0 S4U authentication by default

- This simple and official method replaces cyglsa and "create token"
  methods.  No network share access, same as before.

- lsaauth and create_token are disabled now.  If problems crop up,
  they can be easily reactivated.  If no problems crop up, they
  can be removed in a while, together with the lsaauth subdir.

- Bump Cygwin version to 3.0.

Signed-off-by: Corinna Vinschen <corinna@vinschen.de>

winsup/cygwin/security.h

@@ -479,6 +479,8 @@ HANDLE create_token (cygsid &usersid, user_groups &groups);
 HANDLE lsaauth (cygsid &, user_groups &);
 /* LSA private key storage authentication, same as when using service logons. */
 HANDLE lsaprivkeyauth (struct passwd *pw);
+/* Kerberos or MsV1 S4U logon. */
+HANDLE s4uauth (struct passwd *pw);
 /* Verify an existing token */
 bool verify_token (HANDLE token, cygsid &usersid, user_groups &groups, bool *pintern = NULL);
 /* Get groups of a user */