Convenience macro for libssh2_userauth_publickey_fromfile_ex(3) calls
#include <libssh2.h>
int libssh2_userauth_publickey_fromfile(LIBSSH2_SESSION *session,
                                    const char *username,
                                    const char *publickey,
                                    const char *privatekey,
                                    const char *passphrase);
        This is a macro defined in a public libssh2 header file that is using the underlying function libssh2_userauth_publickey_fromfile_ex(3).