am bf6c2dbe: Merge "Fix mac build."

#include <inttypes.h>

#include <stdint.h>

#include <ucontext.h>

#include <string>

#include <vector>

// Forward declarations.

class BacktraceImpl;

struct ucontext;

typedef ucontext ucontext_t;

class Backtrace {

public:

  // Create the correct Backtrace object based on what is to be unwound.