regexp: Hide debugging code behind DEBUG_REGEXP

xmlRegexpPrint is now a deprecated no-op.

include/libxml/xmlregexp.h

@@ -47,6 +47,7 @@ XMLPUBFUN void			 xmlRegFreeRegexp(xmlRegexpPtr regexp);
 XMLPUBFUN int
 		    xmlRegexpExec	(xmlRegexpPtr comp,
 					 const xmlChar *value);
+XML_DEPRECATED
 XMLPUBFUN void
 		    xmlRegexpPrint	(FILE *output,
 					 xmlRegexpPtr regexp);