Handle colored emojis

[liZe]

Emojis are supported, as long as they’re "normal" characters. Colored emojis are not supported anymore, now that we don’t use Cairo.

As many default fontconfig configurations try to always use colored emojis everywhere, this problem leads to invisible characters when a font with colored emojis is installed. That’s bad 😒. Having monochrome emojis even when colored fonts are installed could be a first step.

(Related to #1338) There are two different formats for colored emojis: one with raster images (used almost everywhere, was working with Cairo), one with vector images (called SVGinOT, but only supported by a small number of applications, not in Cairo). Supporting both of them would be awesome.

[liZe]

Fixed by #1434.