mk/server.mk: add babel and exporter files in contrib to elpaplus

* mk/server.mk (elpaplus-dirty elpaplus-up): Add babel and exporter
  files in contrib by extending ORG_ADD_CONTRIB with their
  prefix-globs.

mk/server.mk

@@ -80,7 +80,7 @@ archive-contents:
 	echo "   (org-plus-contrib . [($(PKG_TAG)) ($(PKG_REQ)) \"$(PKG_DOC)\" tar]))" >> $@
 
 elpaplus:		cleanall info card elpaplus-dirty
-elpaplus-dirty elpaplus-up:	ORG_ADD_CONTRIB=org-*
+elpaplus-dirty elpaplus-up:	ORG_ADD_CONTRIB=org-* ob-* ox-*
 elpaplus-dirty elpaplus-up:	ORGDIR=org-plus-contrib-$(PKG_TAG)
 elpaplus-dirty:
 	@$(MAKE) GITVERSION=$(GITVERSION:release_%=%)-elpaplus version autoloads