libssh2 1.7.0

This release includes the following changes:

 o libssh2_session_set_last_error: Add function
 o mac: Add support for HMAC-SHA-256 and HMAC-SHA-512
 o WinCNG: support for SHA256/512 HMAC
 o kex: Added diffie-hellman-group-exchange-sha256 support
 o OS/400 crypto library QC3 support

This release includes the following security advisory:

 o diffie_hellman_sha256: convert bytes to bits
   CVE-2016-0787: http://www.libssh2.org/adv_20160223.html

This release includes the following bugfixes:

 o SFTP: Increase speed and datasize in SFTP read
 o openssl: make libssh2_sha1 return error code
 o openssl: fix memleak in _libssh2_dsa_sha1_verify()
 o cmake: include CMake files in the release tarballs
 o Fix builds with Visual Studio 2015
 o hostkey.c: Fix compiling error when OPENSSL_NO_MD5 is defined
 o GNUmakefile: add support for LIBSSH2_LDFLAG_EXTRAS
 o GNUmakefile: add -m64 CFLAGS when targeting mingw64
 o kex: free server host key before allocating it (again)
 o SCP: add libssh2_scp_recv2 to support large (> 2GB) files on windows
 o channel: Detect bad usage of libssh2_channel_process_startup
 o userauth: Fix off by one error when reading public key file
 o kex: removed dupe entry from libssh2_kex_methods
 o _libssh2_error: Support allocating the error message
 o hostkey: fix invalid memory access if libssh2_dsa_new fails
 o hostkey: align code path of ssh_rsa_init to ssh_dss_init
 o libssh2.pc.in: fix the output of pkg-config --libs
 o wincng: fixed possible memory leak in _libssh2_wincng_hash
 o wincng: fixed _libssh2_wincng_hash_final return value
 o add OpenSSL 1.1.0-pre2 compatibility
 o agent_disconnect_unix: unset the agent fd after closing it
 o sftp: stop reading when buffer is full
 o sftp: Send at least one read request before reading
 o sftp: Don't return EAGAIN if data was written to buffer
 o sftp: Check read packet file offset
 o configure: build "silent" if possible
 o openssl: add OpenSSL 1.1.0-pre3-dev compatibility
 o GNUmakefile: list system libs after user libs
 
This release would not have looked like this without help, code, reports and
advice from friends like these:

  Alexander Lamaison, Andreas Schneider, brian m. carlson, Daniel Stenberg,
  David Byron, Jakob Egger, Kamil Dudka, Marc Hoersken, Mizunashi Mana,
  Patrick Monnerat, Paul Howarth, Salvador Fandino, Salvador Fandiño,
  Salvador Fandiño, Viktor Szakats, Will Cosgrove,
  (16 contributors)

        Thanks! (and sorry if I forgot to mention someone)
