Re #5552. A safer way of locking the mutex.

In particular, trying to unlock it after the return statement is
not going to work out well.
This might also get this compiling with gcc 4.7.

Code/Mantid/Framework/MDEvents/inc/MantidMDEvents/BoxCtrlChangesList.h

@@ -51,9 +51,8 @@ namespace MDEvents
  public:
    void addBoxToSplit(const T &theBox)
     {
-      m_boxesToSplitMutex.lock();
+      Kernel::Mutex::ScopedLock _lock(m_boxesToSplitMutex);
       m_boxesToSplit.push_back(theBox);
-      m_boxesToSplitMutex.unlock();
     }
 
     //-----------------------------------------------------------------------------------
@@ -72,18 +71,17 @@ namespace MDEvents
     template<class MDBoxToChange >
     std::vector< MDBoxToChange > getBoxesToSplit()const
     {
-      m_boxesToSplitMutex.lock();
+      Kernel::Mutex::ScopedLock _lock(m_boxesToSplitMutex);
       return m_boxesToSplit;
-      m_boxesToSplitMutex.unlock();
     }
     //-----------------------------------------------------------------------------------
     /** Clears the list of boxes that are big enough to split */
     void clearBoxesToSplit()
     {
-      m_boxesToSplitMutex.lock();
+      Kernel::Mutex::ScopedLock _lock(m_boxesToSplitMutex);
       m_boxesToSplit.clear();
-      m_boxesToSplitMutex.unlock();
     }
+
     /**Copy constructor from a box controller pointer */
     BoxCtrlChangesList(const API::BoxController & theController):
     BoxController(theController)
@@ -103,7 +101,7 @@ namespace MDEvents
     BoxCtrlChangesList(size_t nd):BoxController(nd){};
 
  private:
-//
+
     /// Mutex for modifying the m_boxesToSplit member
     Mantid::Kernel::Mutex m_boxesToSplitMutex;
 
@@ -113,4 +111,4 @@ namespace MDEvents
 
 }
 }
-#endif
+#endif