On svn-auth-x509 branch, Support GeneralizedTime format for validity dates.

* subversion/tests/libsvn_subr/x509-test.c
  (cert_tests): Add a cert with a GeneralizedTime format date.

* subversion/libsvn_subr/x509.h
  (ASN1_GENERALIZED_TIME): New macro.
  (x509_utc_to_apr_time): Remove function.
  (x509_get_date): New function, that supports retrieving one date
    in UTCTime or GeneralizedTime and converts it to an apr_time_t.  While
    doing this get rid of the static buffer and memset/memcpy.  Use the
    more specific apr_time_exp_gmt_get() in preference to the ambigously
    named apr_time_exp_get().
  (x509_get_dates): Use x509_get_date(), reorder arguments to our norm of
    output arguments coming first, take a scratch_pool argument.
  (svn_x509_parse_cert): Update x509_get_dates() calls to the new signature.


git-svn-id: https://svn.apache.org/repos/asf/subversion/branches/svn-auth-x509@1606252 13f79535-47bb-0310-9956-ffa450edef68