X-Cart W3C validation fail

X-Cart software is claimed to be W3C compliant, however it does not pass the validation in some cases with specific settings set up.

If you try to enable clean urls functionality, category pages will not meet W3C compliance rules. The reason for that is in a function func_qs_combine used in include/func/func.core.php file. The following part of the code should be replaced:

	return ($qappend ? '?' : '') . join("&", $qs);

with this one:

	return ($qappend ? '?' : '') . join("&", $qs);

This fix resolves the problem with W3C validation.