Remove unnecessary 'extern's.

Change-Id: Iba2b3fb6ff88e504f1657b915120ae43d58a1e03
diff --git a/libc/include/sys/klog.h b/libc/include/sys/klog.h
index acfaa20..47eb3a4 100644
--- a/libc/include/sys/klog.h
+++ b/libc/include/sys/klog.h
@@ -46,7 +46,7 @@
 #define KLOG_SIZE_UNREAD   9
 #define KLOG_SIZE_BUFFER   10
 
-extern int klogctl(int, char *, int);
+int klogctl(int, char *, int);
 
 __END_DECLS