Update lasso to 2.5.1

Changes since 2.4.1 from NEWS file:

2.5.1 - February 19th 2016
---------------------------
17 commits, 16 files changed, 1096 insertions, 42 deletions

- Add missing urn constants used in PAOS HTTP header
- Set NotBefore in SAML 2.0 login assertions
- tests: fix leak in test test16_test_get_issuer
- id-ff: fix leak of profile->private_data->message_id
- saml-2.0: fix leak of message_id in
  lasso_profile_saml20_build_paos_request_msg
- tests: fix leaks in test_ecp
- xml: fix wrong termination of comment
- xml: fix leak in lasso_soap_envelope_new_full
- profile: fix leak of private idp_list field
- saml-2.0: fix leaks of url
- tests: fix leak
- tests: update valgrind suppressions
- perl: remove quotes from $PERL -V::ccflags: output (#9572)
- Fix wrong snippet type (fixes #9616). Thanks to Brett Gardner for the patch.
- tools.c: use correct NID and digest length when building RSA signature
  using SHA-2 digest
  (fixes #10019) Thanks to Brett Gardner for the patch.
- bindings/php5: fix enum getters and setters (fixes #10032). Thanks to
  Brett Gardner for the bug report.
- fix warning about INCLUDES directive

2.5.0 - September 2nd 2015
--------------------------
151 commits, 180 files changed, 8391 insertions, 1339 deletions

- lots of bugfixes (reported by static analysis tools like clang,
  coverity and manual inspection) thanks to Simo Sorce and John Dennis from
  RedHat
- xsd:choices are now parsed correctly by implementing a real finite automata
  for parsing XML documents. New flag for jumping forward and backward in
  schema snippets have been added. It fixes parsing of message from third
  party not following the ordre from the schema (they are entitled to do it but
  most SAML implementations do not)
- added C CGI examples for SP and IdP side
- removed the _POSIX_SOURCE declaration
- added support for the SHA-2 family of hash functions
- fixed protocol profile selection when parsing AuthnRequest
- added support for Python 3, thanks to Houzefa Abbasbhay from
  XCG Consulting
- fixed default value of WantAuthnRequestSigned in metadata parsing
- SAML 2.0 ECP is now functionnal, thanks to John Dennis from RedHat
- added two new API function to LassoProfile to extract the Issuer and
  InResponseTo attribute of messages, allowing pre-treatment before parsing
  the message, to load the metadata of the remote provider, or find the request
  which the response matches.
- fixed segfault when parsing HTTP-Redirect marlformed base64 content
- added support for automake 1.15 (jdennis)

(manu)