Extreme resize test
oiiotool: More careful selection of filter for resizing.

Previously, in cases of large maxification (zooming in), the entire
filter could fail to cover any source pixels, resulting in black grid
lines in the output.  Now we make sure that when the destination pixels
are higher frequency than the source pixels, that the filter is
constructed to be wide enough in "source pixel space."
testsuite ref images for new resize tests
Ensure uniform printing of nan and inf
Helps to make certain testsuite output identical cross-platform (fewer
spurious failures due to printf differences)