Use AM_CPPFLAGS instead of INCLUDES; upgrade gint
Clean up unused variables.
Improve tls support

Remove deprecated types and function calls. Make cipher, mac, and other
priorities configurable.

* include/mailutils/sys/tls-stream.h (_mu_tls_stream): Use gnutls_session_t.
* include/mailutils/tls.h (mu_tls_module_config): New member: priorities.
* libmu_auth/tls.c: Remove deprecated types.
(intialize_tls_session): Make priorities configurable.
(prepare_client_session): Set default priorities.
* libmu_cfg/tls.c: New configuration statement: ssl-priorities.
imap client: fix handling of ID response without untagged part

* libproto/imap/id.c: Make sure returned mu_assoc_t is valid
even if no untagged response was received (equivalent to NIL).
Fix compilation without gnutls

* imap4d/imap4d.c [WITH_TLS] (cb_tls_required): Conditional compilation.
* imap4d/imap4d.h [!WITH_TLS] (tls_encryption_on): Empty define.
* pop3d/pop3d.c [!WITH_TLS] (tls_available): Empty define.
* libmu_scm/mu_mailbox.c (mu_scm_mailbox_print): Fix format string.