Revert of Non-SFI mode: Add Linux asynchronous signal support

src/public/nonsfi/irt_signal_handling.h

Index: src/public/nonsfi/irt_signal_handling.h
diff --git a/src/public/nonsfi/irt_signal_handling.h b/src/public/nonsfi/irt_signal_handling.h
deleted file mode 100644
index a276bdfce6fd74d098cc078b95e51561fe7ce48a..0000000000000000000000000000000000000000
--- a/src/public/nonsfi/irt_signal_handling.h
+++ /dev/null
@@ -1,22 +0,0 @@
-/*
- * Copyright (c) 2015 The Native Client Authors. All rights reserved.
- * Use of this source code is governed by a BSD-style license that can be
- * found in the LICENSE file.
- */
-
-#ifndef NATIVE_CLIENT_SRC_PUBLIC_NONSFI_IRT_SIGNAL_HANDLING_H_
-#define NATIVE_CLIENT_SRC_PUBLIC_NONSFI_IRT_SIGNAL_HANDLING_H_ 1
-
-#include "native_client/src/include/nacl_base.h"
-
-EXTERN_C_BEGIN
-
-/*
- * Initialize signal handler for exceptions and async signals at startup
- * before entering sandbox.
- */
-void nonsfi_initialize_signal_handler(void);
-
-EXTERN_C_END
-
-#endif