testtex --minthreads and --lowtrials (#3418)
testtex --minthreads and --lowtrials (#3418)

When doing thread "wedge" tests, most of the time spent is for the
1-thread case. Who cares about 1 thread anyway? So we make two
improvements with new command line options:

* --minthreads sets the minimum number of threads that will be
  used. For example, `--minthreads 2` will skip the single-thread case
  and start the wedge with the 2 thread case.

* --lowtrials is an optional maximum number of trials just for the 1
  or 2-thread case (overriding --trials just for those thread counts,
  if it is a lower value).

By default, the old behavior is still the default. But these allow a
bit of customization in the tradeoff of how much time to invest in the
very low thread counts in a wedge of thread timings.
OpenImageIO/oiio,OpenImageIO/oiio,lgritz/oiio,lgritz/oiio,lgritz/oiio,OpenImageIO/oiio,OpenImageIO/oiio,lgritz/oiio