Version bump to 5.1.3rc1
unit-tests: Fix memory leak in ntru tests
travis: Run the "all" test case with leak detective enabled

But disable the gcrypt plugin, as it causes leaks.

Also disable the backtraces by libunwind as they seem to cause
threads to get cleaned up after the leak detective already has been
disabled, which leads to invalid free()s.
unit-tests: Fix filtered enumerator tests on 64-bit big-endian platforms

In case of sizeof(void*) == 8 and sizeof(int) == 4 on big-endian hosts
the tests failed as the actual integer value got cut off.
Renewed self-signed OCSP signer certificate
Added libipsec/net2net-3des scenario
ac: Remove unimplemented equals_holder() method from ac_t
x509: Fix some whitespaces and do some minor style cleanups in acert
x509: Skip parsing of acert chargingIdentity, as we don't use it anyway
x509: Replace fixed acert group string getter by a more dynamic group enumerator
x509: Integrate IETF attribute handling, and obsolete ietf_attributes_t

The ietf_attributes_t class is used for attribute certificates only these days,
and integrating them to x509_ac_t simplifies things significantly.
x509: Replace the comma separated string AC group builder with a list based one
pem: Support encoding of attribute certificates

While there is no widely used PEM header for attribute certificates, at least
IAIK-JCE uses BEGIN ATTRIBUTE CERTIFICATE:

  http://javadoc.iaik.tugraz.at/iaik_jce/current/iaik/utils/Util.html#toPemString(iaik.x509.attr.AttributeCertificate)
pki: Don't generate negative random serial numbers in X.509 certificates

According to RFC 5280 4.1.2.2 we MUST force non-negative serial numbers.
pki: Support printing attribute certificates
pki: Implement an acert command to issue attribute certificates
pki: Add acert and extend pki/print manpages
x509: Match acert has_subject() against entityName or holder serial

This allows us to find attribute certificates for a subject certificate in
credential sets.
acert: Implement a plugin finding, validating and evaluating attribute certs

This validator checks for any attribute certificate it can find for validated
end entity certificates and tries to extract group membership information
used for connection authorization rules.
auth-cfg: Declare an attribute certificate helper type to exchange acerts