Update to 1.4.2
    
    - New upstream release 1.4.2
      - Return LIBSSH2_ERROR_SOCKET_DISCONNECT on EOF when reading banner
      - userauth.c: fread() from public key file to correctly detect any errors
      - configure.ac: add option to disable build of the example applications
      - added 'Requires.private:' line to libssh2.pc
      - SFTP: filter off incoming "zombie" responses
      - gettimeofday: no need for a replacement under cygwin
      - SSH_MSG_CHANNEL_REQUEST: default to want_reply
      - win32/libssh2_config.h: remove hardcoded #define LIBSSH2_HAVE_ZLIB