NAME
        ExtendFont -- ensure tf_Extension has been built for a font (V36)

   SYNOPSIS
        success = ExtendFont(font, fontTags)
        D0                   A0    A1

        ULONG ExtendFont(struct textfont *, struct tagitem *);

        success = ExtendFontTags(font, Tag1, ...)  (V39)

        ULONG ExtendFontTags(struct textfont *, ulong, ...);

   FUNCTION
        To extend a textfont structure.

   INPUTS
        font - The font to extend.
        fontTags - An optional taglist.  If NULL, then a default is used.
                   Currently, the only tag defined is TA_DeviceDPI.

   RESULT
        success - 1 if the textfont was properly extended, else 0.

   NOTES
        The varargs stub was missing from amiga.lib until V39.

   SEE ALSO
        graphics/text.h