Various changes suggested by cppcheck

- remove unused variables
- reduce the scope where it makes sense
- correct limits (did you know that strcat()'s last parameter does not
  include the \0 that is always added?)
- set some free()'d pointers to NULL

Source/Core/Common/ExtendedTrace.cpp

@@ -362,8 +362,6 @@ void StackTrace(HANDLE hThread, const char* lpszMessage, FILE *file, DWORD eip,
 {
 	STACKFRAME     callStack;
 	BOOL           bResult;
-	TCHAR          symInfo[BUFFERSIZE] = _T("?");
-	TCHAR          srcInfo[BUFFERSIZE] = _T("?");
 	HANDLE         hProcess = GetCurrentProcess();
 
 	// If it's not this thread, let's suspend it, and resume it at the end