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

diff --git a/coreutils/head.c b/coreutils/head.c
index af9e9f4..6293077 100644
--- a/coreutils/head.c
+++ b/coreutils/head.c
@@ -31,7 +31,7 @@
 
 static const char header_fmt_str[] ALIGN1 = "\n==> %s <==\n";
 
-int head_main(int argc, char **argv);
+int head_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 int head_main(int argc, char **argv)
 {
 	unsigned long count = 10;