[WIN32] implemented a poor man's stacktrace for windows.

Just prints the stacktrace of the current thread into a file. It's still missing the function parameters but it could be extended to print all running threads.
Sample output:
```
Thread 2416 (process 6068)
# 0 CApplication::FrameMove at c:\development\xbmc\xbmc\application.cpp:2948
# 1 CGUIWindowManager::ProcessRenderLoop at c:\development\xbmc\xbmc\guilib\guiwindowmanager.cpp:666
# 2 CGUIWindowManager::CloseWindowSync at c:\development\xbmc\xbmc\guilib\guiwindowmanager.cpp:997
# 3 CGUIWindowManager::ActivateWindow_Internal at c:\development\xbmc\xbmc\guilib\guiwindowmanager.cpp:417
# 4 CGUIWindowManager::ActivateWindow at c:\development\xbmc\xbmc\guilib\guiwindowmanager.cpp:351
# 5 CBuiltins::Execute at c:\development\xbmc\xbmc\interfaces\builtins.cpp:350
# 6 CApplication::ExecuteXBMCAction at c:\development\xbmc\xbmc\application.cpp:5058
# 7 CApplication::OnMessage at c:\development\xbmc\xbmc\application.cpp:5042
# 8 CGUIWindowManager::SendMessageA at c:\development\xbmc\xbmc\guilib\guiwindowmanager.cpp:77
# 9 CGUIWindowManager::DispatchThreadMessages at c:\development\xbmc\xbmc\guilib\guiwindowmanager.cpp:808
#10 CApplication::Process at c:\development\xbmc\xbmc\application.cpp:5096
#11 CXBApplicationEx::Run at c:\development\xbmc\xbmc\xbapplicationex.cpp:111
#12 WinMain at c:\development\xbmc\xbmc\win32\xbmc_pc.cpp:164
#13 __tmainCRTStartup at f:\dd\vctools\crt_bld\self_x86\crt\src\crt0.c:275
#14 WinMainCRTStartup at f:\dd\vctools\crt_bld\self_x86\crt\src\crt0.c:189
#15 BaseThreadInitThunk
#16 RtlInitializeExceptionChain
#17 RtlInitializeExceptionChai
```