((featurep 'gtk)
(concat ", GTK+ Version " gtk-version-string))
((featurep 'x-toolkit) ", X toolkit")
+ ((featurep 'ns-windowing)
+ (format ", *Step %s" ns-version-string))
((boundp 'mac-carbon-version-string)
(concat ", Carbon Version " mac-carbon-version-string))
(t ""))