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

diff --git a/networking/slattach.c b/networking/slattach.c
index ce6d705..17df4fa 100644
--- a/networking/slattach.c
+++ b/networking/slattach.c
@@ -119,7 +119,7 @@
 	restore_state_and_exit(0);
 }
 
-int slattach_main(int argc, char **argv);
+int slattach_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 int slattach_main(int argc, char **argv)
 {
 	/* Line discipline code table */