Dedicated xml,json,yang and xsl parser utility programs added

Sanity check of stdarg (...) added
Cleanup of error messages.

test/test_json.sh

@@ -0,0 +1,14 @@
+#!/bin/bash
+# Test: JSON parser tests
+PROG=../lib/src/clixon_util_json
+
+# include err() and new() functions and creates $dir
+. ./lib.sh
+
+new "json parse"
+expecteof $PROG 0 '{"foo": -23}' "^<foo>-23</foo>$"
+
+new "json parse list"
+expecteof $PROG 0 '{"a":[0,1,2,3]}' "^<a>0</a><a>1</a><a>2</a><a>3</a>$"
+
+rm -rf $dir