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

diff --git a/editors/diff.c b/editors/diff.c
index 3a694e0..c158c87 100644
--- a/editors/diff.c
+++ b/editors/diff.c
@@ -1207,7 +1207,7 @@
 #endif
 
 
-int diff_main(int argc, char **argv);
+int diff_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 int diff_main(int argc, char **argv)
 {
 	bool gotstdin = 0;