Applied patch from Brent Hendricks adding support for late DTD validation.

* python/generator.py python/libxml.c python/libxml2class.txt
  python/libxml_wrap.h python/types.c: Applied patch from Brent
  Hendricks adding support for late DTD validation.
* python/tests/Makefile.am python/tests/dtdvalid.py
  python/tests/test.dtd: integrated the provided regression test
Daniel
diff --git a/config.h.in b/config.h.in
index 8a65287..590e0ce 100644
--- a/config.h.in
+++ b/config.h.in
@@ -25,6 +25,9 @@
 /* Define to 1 if you have the <arpa/nameser.h> header file. */
 #undef HAVE_ARPA_NAMESER_H
 
+/* Whether struct sockaddr::__ss_family exists */
+#undef HAVE_BROKEN_SS_FAMILY
+
 /* Define to 1 if you have the `class' function. */
 #undef HAVE_CLASS
 
@@ -279,5 +282,8 @@
 /* Win32 Std C name mangling work-around */
 #undef snprintf
 
+/* ss_family is not defined here, use __ss_family instead */
+#undef ss_family
+
 /* Win32 Std C name mangling work-around */
 #undef vsnprintf