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/Makefile b/src/po/Makefile
index 9dfbc34..fbe474b 100644
--- a/src/po/Makefile
+++ b/src/po/Makefile
@@ -204,10 +204,12 @@
 	vim.desktop.in
 
 PO_VIM_INPUTLIST = \
-	../../runtime/optwin.vim
+	../../runtime/optwin.vim \
+	../../runtime/defaults.vim
 
 PO_VIM_JSLIST = \
-	optwin.js
+	optwin.js \
+	defaults.js
 
 $(PACKAGE).pot: $(PO_INPUTLIST) $(PO_VIM_INPUTLIST)
 	# Convert the Vim scripts to (what looks like) Javascript