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

diff --git a/networking/nslookup.c b/networking/nslookup.c
index fab7e3e..183ae15 100644
--- a/networking/nslookup.c
+++ b/networking/nslookup.c
@@ -127,7 +127,7 @@
 	}
 }
 
-int nslookup_main(int argc, char **argv);
+int nslookup_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 int nslookup_main(int argc, char **argv)
 {
 	/* We allow 1 or 2 arguments.