Comment 58 for bug 19066

Compared to the previous patch, the on in comment 25 uses logical width instead
of ink width. That's the expected behavior. It also has a little optimization,
dropping an strlen.

The rest of the MathML was not working simply because Pango was refusing to
choose font/shaper for Private Use characters. That was a one-line fix. With
that, it only was not rendering the THIN SPACE character. That's this bug:

  http://bugzilla.gnome.org/show_bug.cgi?id=145275

I also worked around it by making Pango choose font/shaper for space characters
too. All this is in Pango 1.14.1 that is in Rawhide already.

With these, I get Pango render the MathML Torture Test exactly like the Xft
backend. I even changed Pango to use a fixed 96 dpi resolution and got an image
that had only 14 pixel differences with the Xft one, and those are minimal
antialiasing differencing for the letter Pi. (Attaching all in a minute)