libssh2_version - return the libssh2 version number

       This  function  was  added  in libssh2 1.1, in previous versions there way no way to extract this info in
       run-time.

libssh2                                            23 Feb 2009                                libssh2_version(3)

       If  required_version  is  lower  than  or  equal to the version number of the libssh2 in use, the version
       number of libssh2 is returned as a pointer to a zero terminated string.

       The required_version should be the version number as constructed by the LIBSSH2_VERSION_NUM define in the
       libssh2.h public header file, which is a 24 bit number in the 0xMMmmpp format. MM for major, mm for minor
       and pp for patch number.

       To make sure you run with the correct libssh2 version:

       if(!libssh2_version(LIBSSH2_VERSION_NUM)) {
         fprintf(stderr, "Runtime libssh2 version too old.");
         exit(1);
       }

       Unconditionally get the version number:

       printf("libssh2 version: %s", libssh2_version(0));

       libssh2_version - return the libssh2 version number

       The version number of libssh2 is returned as a pointer to  a  zero  terminated  string  or  NULL  if  the
       required_version is not fulfilled.

       #include <libssh2.h>

       const char *
       libssh2_version(int required_version);