cairo: Fix values of prop_em_width, fixed_width.

cairo: Fix values of prop_em_width, fixed_width.

For some reason prop_em_width and fixed_width were getting very small
values, e.g. 5 and 7, when they were being pulled from the font metrics.
These values should be more like 1024 times larger and  I can't figure
why they aren't.  But this works around the problem for now.