Add old release do AppVeyor

RLumSK · RLumSK · commit 28c6d2532ff0 · 2020-05-27T17:53:23.000+02:00
diff --git a/appveyor.yml b/appveyor.yml
@@ -26,6 +26,8 @@ environment:
 
   - R_VERSION: stable
 
+  - R_VERSION: oldrel
+
 build_script:
   - travis-tool.sh install_deps
 
