cairo: fix builds with libpng 1.6

libpng 1.6 emits more warnings than before, and is also stricter with function
ordering.  Fix the function ordering when reading PNGs, and stop treating all
warnings as errors.

Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
runqemu-internal: Drop distcc support

The distcc support is clearly unused and broken, might as well drop the
remaining code fragements.

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>