Various makefile fixes for the test environment.

diff --git a/Make.rules.in b/Make.rules.in
index 5fb5d79..33365bc 100644
--- a/Make.rules.in
+++ b/Make.rules.in
@@ -259,6 +259,9 @@
 
 check test:: $(TESTRESULTS)
 
+$(SUBDIRS:%=%/__test__): dummy
+	@cd `dirname $@` && $(MAKE) test
+
 $(PLTESTS:.c=.ok): $(WINETEST)
 $(CTESTS:.c=.ok): $(TESTPROGRAM).so