Add some old code, do some buildfixing

base/backtrace.cpp

@@ -0,0 +1,17 @@
+#include "base/backtrace.h"
+
+#ifndef _MSC_VER
+
+// LINUX ONLY
+
+#include <execinfo.h>
+#include <unistd.h>
+
+static void *backtrace_buffer[128];
+
+void PrintBacktraceToStderr() {
+  int num_addrs = backtrace(backtrace_buffer, 128);
+  backtrace_symbols_fd(backtrace_buffer, num_addrs, STDERR_FILENO);
+}
+
+#endif