MISSING: letter-spacing property in gtk-text-tag

[stacksmith]

I don't know the syntax for install-properties function... I wound up duplicating the entire gtk-text-tag definition, and including letter-spacing and letter-spacing-set in the correct alphabetical space like this:

 (letter-spacing
    gtk-text-tag-letter-spacing
    "letter-spacing" "gint" t t)
   (letter-spacing-set
    gtk-text-tag-letter-spacing-set
    "letter-spacing-set" "gboolean" t t)

Tested and works visually.