Fix MSVC2015 build.

extensions/mysql/msvc15hack.c

@@ -1,13 +1,86 @@
+
+#define WIN32_LEAN_AND_MEAN
+#include <Windows.h>
+#include <stdlib.h>
+
+// Fix from from https://stackoverflow.com/a/34655235.
+//
+// __iob_func required by the MySQL we use,
+// but no longer exists in the VS 14.0+ crt.
+
+#pragma comment(lib, "DbgHelp.lib")
+#pragma warning(disable:4091) // 'typedef ': ignored on left of '' when no variable is declared
+#include <DbgHelp.h>
+#include <corecrt_wstdio.h>
+
+#define GET_CURRENT_CONTEXT(c, contextFlags) \
+  do { \
+	c.ContextFlags = contextFlags; \
+	__asm    call x \
+	__asm x: pop eax \
+	__asm    mov c.Eip, eax \
+	__asm    mov c.Ebp, ebp \
+	__asm    mov c.Esp, esp \
+  } while(0);
+
+
+FILE * __cdecl __iob_func(void)
+{
+	CONTEXT c = { 0 };
+	STACKFRAME64 s = { 0 };
+	DWORD imageType;
+	HANDLE hThread = GetCurrentThread();
+	HANDLE hProcess = GetCurrentProcess();
+
+	GET_CURRENT_CONTEXT(c, CONTEXT_FULL);
+
+	imageType = IMAGE_FILE_MACHINE_I386;
+	s.AddrPC.Offset = c.Eip;
+	s.AddrPC.Mode = AddrModeFlat;
+	s.AddrFrame.Offset = c.Ebp;
+	s.AddrFrame.Mode = AddrModeFlat;
+	s.AddrStack.Offset = c.Esp;
+	s.AddrStack.Mode = AddrModeFlat;
+
+	if (!StackWalk64(imageType, hProcess, hThread, &s, &c, NULL, SymFunctionTableAccess64, SymGetModuleBase64, NULL))
+	{
+		return NULL;
+	}
+
+	if (s.AddrReturn.Offset == 0)
+	{
+		return NULL;
+	}
+
+	{
+		unsigned char const * assembly = (unsigned char const *)(s.AddrReturn.Offset);
+
+		if (*assembly == 0x83 && *(assembly + 1) == 0xC0 && (*(assembly + 2) == 0x20 || *(assembly + 2) == 0x40))
+		{
+			if (*(assembly + 2) == 32)
+			{
+				return (FILE*)((unsigned char *)stdout - 32);
+			}
+			if (*(assembly + 2) == 64)
+			{
+				return (FILE*)((unsigned char *)stderr - 64);
+			}
+
+		}
+		else
+		{
+			return stdin;
+		}
+	}
+
+	return NULL;
+}
+
 // Adapted from dosmap.c in Visual Studio 12.0 CRT sources.
 //
 // The _dosmaperr function is required by the MySQL lib we use,
 // but no longer exists in the VS 14.0+ crt.
 
-#define WIN32_LEAN_AND_MEAN
-#include <windows.h>
-
-#include <stdlib.h>
-
 static struct errentry
 {
 	DWORD oscode;      // OS return value