add -fvisibility=hidden to CC flags, mark XXX_main functions
EXTERNALLY_VISIBLE. 5% size reduction of libbusybox.so

diff --git a/procps/renice.c b/procps/renice.c
index b2a9ed7..ab0d3a1 100644
--- a/procps/renice.c
+++ b/procps/renice.c
@@ -26,7 +26,7 @@
 void BUG_bad_PRIO_PGRP(void);
 void BUG_bad_PRIO_USER(void);
 
-int renice_main(int argc, char **argv);
+int renice_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 int renice_main(int argc, char **argv)
 {
 	static const char Xetpriority_msg[] ALIGN1 = "%cetpriority";