Fix test t/*35thrclone.t hang on older < 5.8.9 perls

Original test extension 3e2f434d did not properly copy the nanosleep code
from the main loop below it
Fix t/*10examp.t and t/*19fhtrace.t failing under very high test parallelism

Various versions of these tests end up working on the same file, add
pid-based disambiguator
Merge pull request #8 from perl5-dbi/topic/concurrency_testfixes

topic/concurrency_testfixes