On svn-auth-x509 branch, cleanup the x509.h file.

* subversion/libsvn_subr/x509.h:
  (TROPICSSL_X509_H): Remove sentinel used by TropicSSL
  (SVN_LIBSVN_SUBR_X509_H): New sentinel macro.
  (BADCERT_EXPIRED, BADCERT_REVOKED, BADCERT_CN_MISMATCH, BADCERT_NO_TRUSTED):
    Remove constants for decribing cert validation failures, which we don't do.
  (X509_OUTPUT_DER, X509_OUTPUT_PEM, PEM_LINE_LENGTH, X509_ISSUE, X509_SUBJECT):
    Remove constants used for output certs, which we don't support.
  (OID_CN, OID_PKCS1, OID_PKCS1_RSA, OID_PKCS1_RSA_SHA, OID_PKCS9_EMAIL):
    Remove object id constants we don't use.
  (__cplusplus): Add the standard extern wrapper.


git-svn-id: https://svn.apache.org/repos/asf/subversion/branches/svn-auth-x509@1606256 13f79535-47bb-0310-9956-ffa450edef68