Log Message:
Update libssh2 to 1.5.0 to address CVE-2015-1782.
http://www.libssh2.org/adv_20150311.html

Set LICENSE.

Changelog:

This release includes the following changes:

 o Added Windows Cryptography API: Next Generation based backend

This release includes the following bugfixes:

 o Security Advisory for CVE-2015-1782, using SSH_MSG_KEXINIT data unbounded
 o missing _libssh2_error in _libssh2_channel_write
 o knownhost: Fix DSS keys being detected as unknown.
 o knownhost: Restore behaviour of `libssh2_knownhost_writeline` with short buffer.
 o libssh2.h: on Windows, a socket is of type SOCKET, not int
 o libssh2_priv.h: a 1 bit bit-field should be unsigned
 o windows build: do not export externals from static library
 o Fixed two potential use-after-frees of the payload buffer
 o Fixed a few memory leaks in error paths
 o userauth: Fixed an attempt to free from stack on error
 o agent_list_identities: Fixed memory leak on OOM
 o knownhosts: Abort if the hosts buffer is too small
 o sftp_close_handle: ensure the handle is always closed
 o channel_close: Close the channel even in the case of errors
 o docs: added missing libssh2_session_handshake.3 file
 o docs: fixed a bunch of typos
 o userauth_password: pass on the underlying error code
 o _libssh2_channel_forward_cancel: accessed struct after free
 o _libssh2_packet_add: avoid using uninitialized memory
 o _libssh2_channel_forward_cancel: avoid memory leaks on error
 o _libssh2_channel_write: client spins on write when window full
 o windows build: fix build errors
 o publickey_packet_receive: avoid junk in returned pointers
 o channel_receive_window_adjust: store windows size always
 o userauth_hostbased_fromfile: zero assign to avoid uninitialized use
 o configure: change LIBS not LDFLAGS when checking for libs
 o agent_connect_unix: make sure there's a trailing zero
 o MinGW build: Fixed redefine warnings.
 o sftpdir.c: added authentication method detection.
 o Watcom build: added support for WinCNG build.
 o configure.ac: replace AM_CONFIG_HEADER with AC_CONFIG_HEADERS
 o sftp_statvfs: fix for servers not supporting statfvs extension
 o knownhost.c: use LIBSSH2_FREE macro instead of free
 o Fixed compilation using mingw-w64
 o knownhost.c: fixed that 'key_type_len' may be used uninitialized
 o configure: Display individual crypto backends on separate lines
 o examples on Windows: check for WSAStartup return code
 o examples on Windows: check for socket return code
 o agent.c: check return code of MapViewOfFile
 o kex.c: fix possible NULL pointer de-reference with session->kex
 o packet.c: fix possible NULL pointer de-reference within listen_state
 o tests on Windows: check for WSAStartup return code
 o userauth.c: improve readability and clarity of for-loops
 o examples on Windows: use native SOCKET-type instead of int
 o packet.c: i < 256 was always true and i would overflow to 0
 o kex.c: make sure mlist is not set to NULL
 o session.c: check return value of session_nonblock in debug mode
 o session.c: check return value of session_nonblock during startup
 o userauth.c: make sure that sp_len is positive and avoid overflows
 o knownhost.c: fix use of uninitialized argument variable wrote
 o openssl: initialise the digest context before calling EVP_DigestInit()
 o libssh2_agent_init: init ->fd to LIBSSH2_INVALID_SOCKET
 o configure.ac: Add zlib to Requires.private in libssh2.pc if using zlib
 o configure.ac: Rework crypto library detection
 o configure.ac: Reorder --with-* options in --help output
 o configure.ac: Call zlib zlib and not libz in text but keep option names
 o Fix non-autotools builds: Always define the LIBSSH2_OPENSSL CPP macro
 o sftp: seek: Don't flush buffers on same offset
 o sftp: statvfs: Along error path, reset the correct 'state' variable.
 o sftp: Add support for fsync (OpenSSH extension).
 o _libssh2_channel_read: fix data drop when out of window
 o comp_method_zlib_decomp: Improve buffer growing algorithm
 o _libssh2_channel_read: Honour window_size_initial
 o window_size: redid window handling for flow control reasons
 o knownhosts: handle unknown key types