Add a custom fontconfig setup and ship Cantarell as part of it.
This should hopefully make it so that the tests always see the
same default font, as long as you have FONTCONFIG_FILE set up
correctly.
Update all affected tests.
The goal is to fix all the context that influences the rendering
of text nodes in the node file. This will help with better font
testing.
The newly accepted properties are
hint-style: none/slight/full
antialias: none/gray
We are omitting font options and values that aren't supported
in GSK or have no influence on the rendering.
Note that these settings will get incorporated in the PangoFont
that gets set on the resulting text node.
Parser tests included.