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

src/nonsfi/linux/irt_signal_handling.h

Index: src/nonsfi/linux/irt_signal_handling.h
diff --git a/src/nonsfi/linux/irt_signal_handling.h b/src/nonsfi/linux/irt_signal_handling.h
deleted file mode 100644
index eff45af24144dd0ed115662a6b89af476b8da7a9..0000000000000000000000000000000000000000
--- a/src/nonsfi/linux/irt_signal_handling.h
+++ /dev/null
@@ -1,23 +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_NONSFI_LINUX_IRT_SIGNAL_HANDLING_H_
-#define NATIVE_CLIENT_SRC_NONSFI_LINUX_IRT_SIGNAL_HANDLING_H_ 1
-
-#include "native_client/src/untrusted/irt/irt.h"
-
-EXTERN_C_BEGIN
-
-/*
- * See documentation for nacl_irt_async_signal_handler members in
- * src/untrusted/irt/irt.h
- */
-int nacl_async_signal_set_handler(NaClIrtAsyncSignalHandler handler);
-int nacl_async_signal_send_async_signal(nacl_irt_tid_t tid);
-
-EXTERN_C_END
-
-#endif