* Regexp improvements

* Added check for libxml in configure';
  * Added clixon_util_regexp utility function
* Yang state get improvements
  * Integrated state and config into same tree on retrieval, not separate trees
  * Added cli functions `cli_show_config_state()` and `cli_show_auto_state()` for showing combined config and state info.
  * Added integrated state in the main example: `interface/oper-state`.
  * Added performance tests for getting state, see [test/test_perf_state.sh].

test/test_datastore.sh

@@ -7,7 +7,6 @@ s="$_" ; . ./lib.sh || if [ "$s" = $0 ]; then exit 0; else return 0; fi
 
 fyang=$dir/ietf-ip.yang
 
-# If set, enable debugging (of backend)
 : ${clixon_util_datastore:=clixon_util_datastore}
 
 cat <<EOF > $fyang