Remove unnecessary 'extern's.

Change-Id: Iba2b3fb6ff88e504f1657b915120ae43d58a1e03
diff --git a/libc/include/bits/fcntl.h b/libc/include/bits/fcntl.h
index 90f933c..604d35a 100644
--- a/libc/include/bits/fcntl.h
+++ b/libc/include/bits/fcntl.h
@@ -33,7 +33,7 @@
 
 __BEGIN_DECLS
 
-extern int fcntl(int, int, ...);
+int fcntl(int, int, ...);
 
 __END_DECLS