tracef: ensure output hits the screen
this slows down, but when tracing performance isn't the primary
objective, seeing all things is...
extern unsigned char mode;
#ifdef ENABLE_TRACE
-#define tracef(...) if (mode & MODE_TRACE) fprintf(stdout, __VA_ARGS__)
+#define tracef(...) if (mode & MODE_TRACE) { fprintf(stdout, __VA_ARGS__); fflush(stdout); }
#else
#define tracef(...) /* noop */
#endif
