Remove the hacks to avoid floating-point issues in the tcpdump checks.

Remove the hacks to avoid floating-point issues in the tcpdump checks.

I can't seem to make those issues pop up on my (x86-64) machine, and, if
they do show up on any platforms, the best hack to handle it is probably
to have a special tcpdump flag to force it to do a floating-point
calculation and see what result is generated, and report the result, so
we know what it'll do with the numbers in the test files, and have
tests/TESTrun run tcpdump with that flag.

If those tests *do* fail, we'll know what calculations to do.