Print out stack trace in mac, too

Summary: While debugging Mac-only issue with ThreadLocalPtr, this was very useful. Let's print out stack trace in MAC OS, too.

Test Plan: Verified that somewhat useful stack trace was generated on mac. Will run PrintStack() on linux, too.

Reviewers: ljin, haobo

Reviewed By: haobo

CC: leveldb

Differential Revision: https://reviews.facebook.net/D18189

port/stack_trace.h

@@ -0,0 +1,19 @@
+//  Copyright (c) 2013, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under the BSD-style license found in the
+//  LICENSE file in the root directory of this source tree. An additional grant
+//  of patent rights can be found in the PATENTS file in the same directory.
+//
+#pragma once
+namespace rocksdb {
+namespace port {
+
+// Install a signal handler to print callstack on the following signals:
+// SIGILL SIGSEGV SIGBUS SIGABRT
+// Currently supports linux only. No-op otherwise.
+void InstallStackTraceHandler();
+
+// Prints stack, skips skip_first_frames frames
+void PrintStack(int first_frames_to_skip = 0);
+
+}  // namespace port
+}  // namespace rocksdb