Rename ssl_set_bio_timeout() to set_bio()

Initially thought it was best to keep the old function around and add a new
one, but this so many ssl_set_xxx() functions are changing anyway...
diff --git a/programs/ssl/ssl_fork_server.c b/programs/ssl/ssl_fork_server.c
index 91f0060..e743e3e 100644
--- a/programs/ssl/ssl_fork_server.c
+++ b/programs/ssl/ssl_fork_server.c
@@ -267,7 +267,7 @@
 
         mbedtls_ssl_set_rng( &ssl, mbedtls_ctr_drbg_random, &ctr_drbg );
         mbedtls_ssl_set_dbg( &conf, my_debug, stdout );
-        mbedtls_ssl_set_bio_timeout( &ssl, &client_fd, mbedtls_net_send, mbedtls_net_recv, NULL );
+        mbedtls_ssl_set_bio( &ssl, &client_fd, mbedtls_net_send, mbedtls_net_recv, NULL );
 
         mbedtls_ssl_set_ca_chain( &conf, srvcert.next, NULL );
         if( ( ret = mbedtls_ssl_set_own_cert( &ssl, &srvcert, &pkey ) ) != 0 )