Add a results.tar.gz target to the test Makefile

Sometimes it is useful to be able to package the result of a run of
the testsuite. This new target creates an archive containing the html
page and at least all the files it links to.

The archive might contain some unneeded images.

test/Makefile.am

@@ -1813,6 +1813,17 @@ check-ref-missing:
 
 release-verify-sane-tests: check-ref-missing
 
+results.tar:
+	@tar cf $@ index.html testtable.js *.log; \
+	for i in output/*.fail.png ; do \
+		testname=$${i#output/} ; \
+		testname=$${testname%%.*} ; \
+		tar uf $@ $${testname}*.ref.png $${i%fail.png}out.png $${i%fail.png}diff.png ; \
+	done
+
+results.tar.gz: results.tar
+	gzip -c $< > $@
+
 .PHONY: check-valgrind test recheck retest check-ref-dups check-ref-missing release-verify-sane-tests
 
 EXTRA_DIST += Makefile.win32