This test uses __float128 data type when it is available
for implementing a "perfect" reference implementation. The
output from from pixman_transform_point_31_16() and
pixman_transform_point_31_16_affine() is compared with the
reference implementation to make sure that the rounding
errors may only show up in a single least significant bit.
The platforms and compilers, which do not support __float128
data type, can rely on crc32 checksum for the pseudorandom
transform results.
