* 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].

configure

@@ -4417,6 +4417,54 @@ _ACEOF
 fi
 
 
+# This is for Libxml2 code which we can use for XSD regexp
+# AC_CHECK_HEADERS([libxml2/libxml/xmlexports.h])
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for xmlRegexpCompile in -lxml2" >&5
+$as_echo_n "checking for xmlRegexpCompile in -lxml2... " >&6; }
+if ${ac_cv_lib_xml2_xmlRegexpCompile+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  ac_check_lib_save_LIBS=$LIBS
+LIBS="-lxml2  $LIBS"
+cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+
+/* Override any GCC internal prototype to avoid an error.
+   Use char because int might match the return type of a GCC
+   builtin and then its argument prototype would still apply.  */
+#ifdef __cplusplus
+extern "C"
+#endif
+char xmlRegexpCompile ();
+int
+main ()
+{
+return xmlRegexpCompile ();
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_link "$LINENO"; then :
+  ac_cv_lib_xml2_xmlRegexpCompile=yes
+else
+  ac_cv_lib_xml2_xmlRegexpCompile=no
+fi
+rm -f core conftest.err conftest.$ac_objext \
+    conftest$ac_exeext conftest.$ac_ext
+LIBS=$ac_check_lib_save_LIBS
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_cv_lib_xml2_xmlRegexpCompile" >&5
+$as_echo "$ac_cv_lib_xml2_xmlRegexpCompile" >&6; }
+if test "x$ac_cv_lib_xml2_xmlRegexpCompile" = xyes; then :
+  cat >>confdefs.h <<_ACEOF
+#define HAVE_LIBXML2 1
+_ACEOF
+
+  LIBS="-lxml2 $LIBS"
+
+fi
+
+
 for ac_func in inet_aton sigaction sigvec strlcpy strsep strndup alphasort versionsort
 do :
   as_ac_var=`$as_echo "ac_cv_func_$ac_func" | $as_tr_sh`