GSSAPI key exchange authentication disabled as it caused failures when old version of MIT Kerberos was installed on the machine

(master branch version of the change - different to the dev version in dceed175)

https://winscp.net/tracker/1874

Source commit: a3240866f68b4e053549cf1300e076ad3b99dcb4

source/core/SecureShell.cpp

@@ -262,6 +262,7 @@ Conf * __fastcall TSecureShell::StoreToConfig(TSessionData * Data, bool Simple)
   conf_set_bool(conf, CONF_try_tis_auth, Data->AuthTIS);
   conf_set_bool(conf, CONF_try_ki_auth, Data->AuthKI);
   conf_set_bool(conf, CONF_try_gssapi_auth, Data->AuthGSSAPI);
+  conf_set_bool(conf, CONF_try_gssapi_kex, false);
   conf_set_bool(conf, CONF_gssapifwd, Data->GSSAPIFwdTGT);
   conf_set_bool(conf, CONF_change_username, Data->ChangeUsername);