patch 9.0.1537: message for opening the cmdline window is not translated

Problem:    Message for opening the cmdline window is not translated.
Solution:   Add gettext() and scan the defaults script for text to be
            translated.  (closes #12371)
diff --git a/src/po/tojavascript.vim b/src/po/tojavascript.vim
index 7868570..8b0dd73 100644
--- a/src/po/tojavascript.vim
+++ b/src/po/tojavascript.vim
@@ -8,8 +8,9 @@
 for name in argv()[1:]
   exe 'edit ' .. fnameescape(name)
 
-  " Strip comments
+  " Strip comments, also after :set commands.
   g/^\s*"/s/.*//
+  g/^\s*set .*"/s/.*//
 
   " Write as .js file, xgettext recognizes them
   exe 'w! ' .. fnamemodify(name, ":t:r") .. ".js"