flush output bits immediately to stop pause in BER reports

src/rtl_fsk.c

@@ -174,6 +174,7 @@ static void rtlsdr_callback(unsigned char *buf, uint32_t len, void *ctx)
 			fprintf(stderr, "Short write, bits lost, exiting!\n");
 			rtlsdr_cancel_async(dev);
                     }
+                    if((FILE*)ctx == stdout) fflush((FILE*)ctx);
 
                     if (dashboard) {
                         /* update buffer of timing samples */