quick but apparently working implementation of xi:fallback, should close

* xinclude.c: quick but apparently working implementation of
  xi:fallback, should close bug #89684
* Makefile.am test/XInclude/docs/fallback.xml
  result/XInclude/fallback.xml: added a basic test for fallback,
  and run with --nowarning to avoid a spurious warning
* configure.in: applied patch from Frederic Crozat for python
  bindings on AMD 64bits machines.
Daniel
diff --git a/Makefile.am b/Makefile.am
index 0d3162f..f9d9426 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -399,10 +399,10 @@
 	  if [ ! -d $$i ] ; then \
 	  if [ ! -f $(srcdir)/result/XInclude/$$name ] ; then \
 	      echo New test file $$name ; \
-	      $(CHECKER) $(top_builddir)/xmllint --xinclude $$i > $(srcdir)/result/XInclude/$$name ; \
+	      $(CHECKER) $(top_builddir)/xmllint --nowarning --xinclude $$i > $(srcdir)/result/XInclude/$$name ; \
 	  else \
 	      echo Testing $$name ; \
-	      $(CHECKER) $(top_builddir)/xmllint --xinclude $$i > result.$$name ; \
+	      $(CHECKER) $(top_builddir)/xmllint --nowarning --xinclude $$i > result.$$name ; \
 	      grep "MORY ALLO" .memdump  | grep -v "MEMORY ALLOCATED : 0";\
 	      diff $(srcdir)/result/XInclude/$$name result.$$name ; \
 	      rm result.$$name ; \