The calculations were wrong.

FreeType makes it really hard to set size and ppem independently.
For now, disable it.  Need to come up with a fix later.

This reverts commit 727135f3.

This is work-in-progress.  Didn't mean to push it out just yet.

Since we use the OpenType versions of Uniscribe functions, we are
relying on that version of the WINNT API.  Otherwise, usp10.h will hide
those symbols.

https://bugs.freedesktop.org/show_bug.cgi?id=50970

Until I figure out the build issues.  Sigh...

Shaves another 3% for DejaVu Sans long Latin strings.

Shaves a good 10% off DejaVu Sans with simple Latin text for me.
Now, DejaVu is very ChainContext-intensive, but it's also a very
popular font!

Makes more sense, optimization-wise.

I know...

I see about 8% speedup with long strings with DejaVu Sans.

This is apparently what Uniscribe does.  Test case is:

  SEEN FATHA TEH ALEF

with Arabic Typesetting.  Originally reported by Khaled Hosny.