*: introduce and use ffulsh_all()

function                                             old     new   delta
buffer_fill_and_print                                179     196     +17
fflush_all                                             -       9      +9
spawn                                                 87      92      +5
rtcwake_main                                         455     453      -2
...
alarm_intr                                            93      84      -9
readcmd                                             1072    1062     -10
bb_ask                                               345     333     -12
more_main                                            845     832     -13
flush_stdout_stderr                                   42      23     -19
xfflush_stdout                                        27       -     -27
flush_stderr                                          30       -     -30
------------------------------------------------------------------------------
(add/remove: 1/2 grow/shrink: 2/50 up/down: 31/-397)         Total: -366 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
diff --git a/libbb/vfork_daemon_rexec.c b/libbb/vfork_daemon_rexec.c
index 27efb0e..9be9017 100644
--- a/libbb/vfork_daemon_rexec.c
+++ b/libbb/vfork_daemon_rexec.c
@@ -25,7 +25,7 @@
 	volatile int failed;
 	pid_t pid;
 
-// Ain't it a good place to fflush(NULL)?
+	fflush_all();
 
 	/* Be nice to nommu machines. */
 	failed = 0;