Fix docbook support with libxml2 >= 2.6.x

(cherry picked from commit c1c8adb7fb)

kxsldbg/kxsldbgpart/libxsldbg/xsldbg.cpp

@@ -975,9 +975,13 @@ xsldbgLoadXmlData(void)
 #endif
 #ifdef LIBXML_DOCB_ENABLED
     if (optionsGetIntOption(OPTIONS_DOCBOOK))
+#       if LIBXML_VERSION >= 20600
+        doc = xmlParseFile((char *) optionsGetStringOption(OPTIONS_DATA_FILE_NAME));
+#       else
         doc = docbParseFile((char *)
                             optionsGetStringOption(OPTIONS_DATA_FILE_NAME),
                             NULL);
+#       endif
     else
 #endif
 
@@ -1027,7 +1031,11 @@ xsldbgLoadXmlTemporary(const xmlChar * path)
 #endif
 #ifdef LIBXML_DOCB_ENABLED
     if (optionsGetIntOption(OPTIONS_DOCBOOK))
+#       if LIBXML_VERSION >= 20600
+        doc = xmlParseFile((char *) path);
+#       else
         doc = docbParseFile((char *) path, NULL);
+#       endif
     else
 #endif
         doc = xmlSAXParseFile(&mySAXhdlr, (char *) path, 0);