Call SymCleanup() in wxStackWalker to fix problem with next call to it.

Calling SymInitialize() second and subsequent times failed (and hence so did
wxStackWalker::WalkFrom() and other methods) as we didn't call SymCleanup()
because of some problems with old versions of debughlp.dll. These problems
don't seem to exist any more so do call SymCleanup() so that we can walk the
stack more than once.

Closes #11544.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@62925 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/msw/stackwalk.cpp

@@ -300,14 +300,10 @@ void wxStackWalker::WalkFrom(const CONTEXT *pCtx, size_t skip, size_t maxDepth)
         }
     }
 
-    // this results in crashes inside ntdll.dll when called from
-    // exception handler ...
-#if 0
     if ( !wxDbgHelpDLL::SymCleanup(hProcess) )
     {
         wxDbgHelpDLL::LogError(wxT("SymCleanup"));
     }
-#endif
 }
 
 void wxStackWalker::WalkFrom(const _EXCEPTION_POINTERS *ep, size_t skip, size_t maxDepth)