Divert log functions to the gpgrt log functions.
* src/misc.c (my_gpgrt_post_fatal_handler): New. (_gcry_set_gpgrt_post_log_handler): New. (map_log_level): New. (_gcry_logv): Use gcrypt log function unless a handler has been installed. * src/global.c (global_init): Install post log handler. * src/gcrypt.h.in (gcry_set_log_handler): Deprecate.