FindGnuTLS.cmake with cmake 2.6
Created by: bmiklautz
Minimum required cmake version is set to 2.6 but 2.6 doesn't contain FindGnuTLS.cmake which is used by remmina-plugins/vnc/libvncserver/CMakeLists.txt.
Version 2.8 of cmake has FindGnuTLS.cmake so remmina should require version 2.8 or ship FindGnuTLS.cmake itself.