[plt-translators] english-string-constants.ss update

Index: $PLTHOME/collects/string-constants/english-string-constants.ss
===================================================================
--- $PLTHOME/collects/string-constants/english-string-constants.ss	(revision 6939)
+++ $PLTHOME/collects/string-constants/english-string-constants.ss	(working copy)
@@ -918,9 +918,12 @@
   (compiling-teachpack "Compiling ~a teachpack ...")
   (teachpack-pre-installed "Preinstalled Teachpacks")
   (teachpack-user-installed "User-installed Teachpacks")
-  (install-teachpack... "Install Teachpack...")
+  (add-teachpack-to-list... "Add Teachpack to List...")
   (teachpack-already-installed "A teachpack with the name '~a' has already been installed. Overwrite it?")
+  ; ~a is filled with a list of language names. Each name is separated by a newline and is indented two spaces (no commas, no 'and')
+  (teachpacks-only-in-languages "Teachpacks are only available in these languages: ~a")
   
+  
  ;;; Language dialog
  (introduction-to-language-dialog
   "Please select a language. Students in most introductory courses should use the default language.")