Followup to r1543992, add the usual deprecated version number.

This feels a tad awkward since gnome_keyring, kwallet and gpg_agent
should all have basically never been added as public APIs and nobody
should have wanted to use them since.  But I guess since we didn't
bother to mark them as deprecated till now they're not until 1.9.

* subversion/include/svn_auth.h
  (svn_auth_get_windows_simple_provider,
   svn_auth_get_windows_ssl_client_cert_pw_provider,
   svn_auth_get_windows_ssl_server_trust_provider,
   svn_auth_get_keychain_simple_provider,
   svn_auth_get_keychain_ssl_client_cert_pw_provider,
   svn_auth_get_gnome_keyring_simple_provider,
   svn_auth_get_gnome_keyring_ssl_client_cert_pw_provider,
   svn_auth_get_kwallet_simple_provider,
   svn_auth_get_kwallet_ssl_client_cert_pw_provider,
   svn_auth_get_gpg_agent_simple_provider): Mark as deprecated in 1.9
   


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1544001 13f79535-47bb-0310-9956-ffa450edef68