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
new file mode 100644
index 0000000000000000000000000000000000000000..a276bdfce6fd74d098cc078b95e51561fe7ce48a
--- /dev/null
+++ b/src/public/nonsfi/irt_signal_handling.h
@@ -0,0 +1,22 @@
+/*
+ * 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