Make named_atomic-test find its sub-process under Windows, too.
Make named_atomic-test find its sub-process under Windows, too.

* subversion/tests/libsvn_subr/named_atomic-test.c
  (run_procs): add a bit of directory magic

jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion