This does the following:
* Adds a baseline argument to get_text_size (the baseline is the
distance from the top of the texture to the baseline).
* Stores the baseline in the container when calculating the title
height.
* Takes the baseline into account when calculating the config's max font
height.
* When rendering, pads the textures according to the baseline so they
line up.
The condition checking if the markup is valid was inverted.
This commit also adds better error handling: if the markup cannot
be parsed, it fallbacks to plain text.
This starts up the event loop and wayland display and shims out the
basic top level rendering concepts. Also includes some changes to
incorporate pango into the 1.x codebase properly.