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

diff --git a/networking/udhcp/dhcpc.c b/networking/udhcp/dhcpc.c
index 21b496c..e00379b 100644
--- a/networking/udhcp/dhcpc.c
+++ b/networking/udhcp/dhcpc.c
@@ -140,7 +140,7 @@
 }
 
 
-int udhcpc_main(int argc, char **argv);
+int udhcpc_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 int udhcpc_main(int argc, char **argv)
 {
 	uint8_t *temp, *message;