[cairo] Speeding up _cairo_fixed_from_double

[Daniel Amelang]

> Keep in mind that configure-time endian checks are unreliable on
> Mac OS X because a single executable may contain objects for multiple
> architectures (right now 32+64 bit Intel and PPC)...

AFAIK, the existence of fat binaries doesn't interfere with autoconf's
job. We're not building fat binaries during the configure stage, and
we don't compile to a fat binary. In addition, that would be a general
autoconf on OS X issue, not a cairo thing.

But thanks for the heads up, I could be wrong.

Dan