[Fontconfig] Support Emoji

[Guo Yunhe (郭云鹤)]

Could fontconfig add Unicode blocks of Emoji? 
https://en.wikipedia.org/wiki/Emoji#Blocks

Then users can specify a font for them:

<match>
   <test name="family">sans-serif</test>
   <test name="lang">emoji</test>
   <edit name="family">My Emoji Font</edit>
</match>

-- 
Guo Yunhe (郭云鹤)
http://guoyunhe.me/