Add new scripts test cases to EXTRA_DIST

scripts/Makefile.am

@@ -79,6 +79,8 @@ EXTRA_DIST = \
 	t/600_Dpkg_Changelog/shadow \
 	t/700_Dpkg_Control.t \
 	t/700_Dpkg_Control/control-1 \
+	t/750_Dpkg_Substvars.t \
+	t/750_Dpkg_Substvars/substvars1 \
 	t/800_Dpkg_IPC.t \
 	t/900_update_alternatives.t