Extract ioctl to <bits/ioctl.h>.

Bug: http://b/28067717
Change-Id: I93625d19fa5a033ab22c650d536e98674f0a8d9d
diff --git a/libc/include/sys/ioctl.h b/libc/include/sys/ioctl.h
index a1014dc..ed261f2 100644
--- a/libc/include/sys/ioctl.h
+++ b/libc/include/sys/ioctl.h
@@ -40,10 +40,6 @@
 #include <sys/ioctl_compat.h>
 #include <linux/tty.h>
 
-__BEGIN_DECLS
-
-extern int ioctl(int, int, ...);
-
-__END_DECLS
+#include <bits/ioctl.h>
 
 #endif /* _SYS_IOCTL_H_ */