does-hunspell-works-under-valgrind: workaround the testcase
echo "NEWSX" | hunspell -a with and w/o valgrind differed in
lower case. This could be workarounded by running such a command
under --tool=none.
Jan Kratochvil suggested the better workaround finding out
spelling suggestions somehow were based on the processor time used by
the process. And so overriding clock to simply always return zero means
the process cannot observe the cpu time used.