On svn-auth-x509 branch, fix comments and remove unused variable.

* subversion/tests/libsvn_subr/x509-test.c
  (x509_test): Fix comment to match implementation.
  (compare_dates): Remove unused matched variable and expand a comment
    slightly for more clarity.


git-svn-id: https://svn.apache.org/repos/asf/subversion/branches/svn-auth-x509@1606248 13f79535-47bb-0310-9956-ffa450edef68