Load fonts from raw data on cairo backend

[JAicewizard]

See https://stackoverflow.com/a/10846042/5799890 for a hacky solution We can also write the font to a tmp file.

Tagging @ForLoveOfCats as they got their name on the note

[khaledhosny]

The code in that link does not do much, the actual code that loads fonts in Pango is in a different file, but this blog post is a better description of what needs to be done http://mces.blogspot.com/2015/05/how-to-use-custom-application-fonts.html