Add support for experimental features New experimental features should have their own configure switch to enable or disable them at compile time. Additionally they can check if the configure variable build_all_experimental_features is set and enable the feature. This variable will be set if the command line option --enable-all-experimental-features is used to configure sssd. This will make it easy to enable all experimental features. Experimental features should be marked in the man pages. To simplify this include/experimental.xml can be used.