On svn-auth-x509 branch, restore Subject output.

* subversion/include/svn_x509.h
  (SVN_X509_CERTINFO_KEY_SUBJECT): New constant.

* subversion/libsvn_subr/x509parse.c
  (svn_x509_parse_cert): Convert the subject data to a Distinguished Name
    string and store it in the certinfo hash.

* subversion/tests/libsvn_subr/x509-test.c
  (x509_test): Remove the cert_name member, add a subject member.
  (cert_tests): Remove cert_name entries and add subject entries.
  (compare_dates): Replace cert_name with subject.
  (compare_results): Verify subject, replace cert_name with subject.

* subversion/svn/auth-cmd.c
  (show_cert): Display subject.


git-svn-id: https://svn.apache.org/repos/asf/subversion/branches/svn-auth-x509@1606270 13f79535-47bb-0310-9956-ffa450edef68