[cairo] pixman configure checks for gtk+

[Behdad Esfahbod]

Hi Soeren,

Seems like pixman looks for Gtk+ during configure, to enable some
interactive tests.  This can make life hard for people trying to build
an entire GNOME stack in an alternative prefix.

I suggest at least a --disable-gtk option be added to pixman's
configure.

Cheers,
-- 
behdad
http://behdad.org/

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