Only set gcrypt thread callback for older version of gcrypt.
* agent/gpg-agent.c, dirmngr/dirmngr.c, g13/g13.c, scd/scdaemon.c (USE_GCRY_THREAD_CBS): New macro, defined if GCRY_THREAD_OPTION_VERSION is 0. (fixed_gcry_pth_init) [!USE_GCRY_THREAD_CBS]: Don't define. (main) [!USE_GCRY_THREAD_CBS]: Do not install thread callbacks.