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

diff --git a/coreutils/who.c b/coreutils/who.c
index 546050a..6e7710c 100644
--- a/coreutils/who.c
+++ b/coreutils/who.c
@@ -39,7 +39,7 @@
 	strcpy(str6, "old");
 }
 
-int who_main(int argc, char **argv);
+int who_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 int who_main(int argc, char **argv)
 {
 	char str6[6];