[HarfBuzz] Support for 'rand' (randomize) feature?

[Khaled Hosny]

As its name suggests, 'rand' is used to list multiple glyph variants
that the engine should select from (pseudo)randomly, see:
http://www.microsoft.com/typography/otspec/features_pt.htm#rand

For testing, my OpenType implementation of Knuth's Punk font can be a
good test:
https://github.com/khaledhosny/punk-otf

(though it is not a serious font, 'rand' can have good application in
calligraphic and fonts that tries to capture irregularities of hand
writing.)

Regards,
 Khaled

-- 
 Khaled Hosny
 Egyptian
 Arab