When clobbering, also clean the docs.

Makefile.pre.in

@@ -1031,13 +1031,17 @@ rmtestturds:
 	-rm -f *.txt
 	-rm -f gb-18030-2000.xml
 
+docclean:
+	-rm -rf Doc/build
+	-rm -rf Doc/tools/sphinx Doc/tools/pygments Doc/tools/docutils
+
 clean: pycremoval
 	find . -name '*.o' -exec rm -f {} ';'
 	find . -name '*.s[ol]' -exec rm -f {} ';'
 	find $(srcdir)/build -name 'fficonfig.h' -exec rm -f {} ';' || true
 	find $(srcdir)/build -name 'fficonfig.py' -exec rm -f {} ';' || true
 
-clobber: clean rmtestturds
+clobber: clean rmtestturds docclean
 	-rm -f $(BUILDPYTHON) $(PGEN) $(LIBRARY) $(LDLIBRARY) $(DLLLIBRARY) \
 		tags TAGS \
 		config.cache config.log pyconfig.h Modules/config.c