CLI show compare example function

Improved diff algorithm for XML and TEXT/curly, replaced UNIX diff with structural in-mem algorithm
Fixed: ["show compare" and "show compare | display cli" differs #23](https://github.com/clicon/clixon-controller/issues/23)
Changed parameters of example clispec function `compare_dbs()`
Added show2cbuf functions for TEXT/CLI
Renamed clixon_txt2file to clixon_text2file

util/clixon_util_xml.c

@@ -334,7 +334,7 @@ main(int    argc,
     /* 4. Output data (xml/json/text) */
     if (output){
         if (textout){
-            if (clixon_txt2file(stdout, xt, 0, fprintf, 1, 0) < 0)
+            if (clixon_text2file(stdout, xt, 0, fprintf, 1, 0) < 0)
                 goto done;
         }
         else if (jsonout){