Initial implementation of scope guard logging for including in crash logs.

This adds a mechanism to create scope guards with an associated std::function
which is called to output diagnostic info in the event of a crash.
Add a macro to make it easy to efficiently capture variables on the stack
and output a formatted message.
Requires C++11, #ifdefed out for legacy compilers.

src/stdafx.h

@@ -520,4 +520,10 @@ static inline void free(const void *ptr)
 	#define IGNORE_UNINITIALIZED_WARNING_STOP
 #endif
 
+#if !defined(DISABLE_SCOPE_INFO) && (__cplusplus >= 201103L || defined(__STDCXX_VERSION__) || defined(__GXX_EXPERIMENTAL_CXX0X__) || defined(__GXX_EXPERIMENTAL_CPP0X__))
+#define USE_SCOPE_INFO
+#endif
+
+#define SINGLE_ARG(...) __VA_ARGS__
+
 #endif /* STDAFX_H */