Bump minimum gtk version to 2.10

That is the version available in RHEL 5. The configure change for
telepathy has been changed for consistency only.

Change-Id: I664901dd2bbcc75f6f6fb84940f3fa85d69f57dd
Reviewed-on: https://gerrit.libreoffice.org/13369
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>