add EIGEN_WORK_AROUND_QT_BUG_CALLING_WRONG_OPERATOR_NEW_FIXED_IN_QT_4_5

an ugly hack that allows people to do QVector<Vector4f> with Qt <= 4.4
the Qt bug this is working around is fixed by Gael in Qt 4.5

Eigen/src/Core/util/Memory.h

@@ -191,6 +191,27 @@ inline static int ei_alignmentOffset(const Scalar* ptr, int maxOffset)
 #define ei_aligned_stack_delete(TYPE,PTR,SIZE) ei_delete_elements_of_array<TYPE>(PTR, SIZE); \
                                                ei_aligned_stack_free(PTR,sizeof(TYPE)*SIZE)
 
+/** Qt <= 4.4 has a bug where it calls new(ptr) T instead of ::new(ptr) T.
+  * This fails as we overload other operator new but not this one. What Qt really means is placement new.
+  * Since this is getting used only with fixed-size Eigen matrices where the ctor does nothing, it is OK to
+  * emulate placement new by just returning the ptr -- no need to call ctors. Good, because we don't know the
+  * class in this macro. So this can safely be used for QVector<Eigen::Vector4f> but definitely not for
+  * QVector<Eigen::VectorXf>.
+  *
+  * This macro will go away as soon as Qt >= 4.5 is prevalent -- most likely it should go away in Eigen 2.1.
+  */
+#ifdef EIGEN_WORK_AROUND_QT_BUG_CALLING_WRONG_OPERATOR_NEW_FIXED_IN_QT_4_5
+#define EIGEN_WORKAROUND_FOR_QT_BUG_CALLING_WRONG_OPERATOR_NEW \
+    void *operator new(size_t, void *ptr) throw() { \
+      return ptr; \
+    } \
+    void *operator new[](size_t, void *ptr) throw() { \
+      return ptr; \
+    }
+#else
+#define EIGEN_WORKAROUND_FOR_QT_BUG_CALLING_WRONG_OPERATOR_NEW
+#endif
+
 /** \brief Overloads the operator new and delete of the class Type with operators that are aligned if NeedsToAlign is true
   *
   * When Eigen's explicit vectorization is enabled, Eigen assumes that some fixed sizes types are aligned
@@ -237,7 +258,8 @@ inline static int ei_alignmentOffset(const Scalar* ptr, int maxOffset)
       return Eigen::ei_conditional_aligned_malloc<NeedsToAlign>(size); \
     } \
     void operator delete(void * ptr) { Eigen::ei_aligned_free(ptr); } \
-    void operator delete[](void * ptr) { Eigen::ei_aligned_free(ptr); }
+    void operator delete[](void * ptr) { Eigen::ei_aligned_free(ptr); } \
+    EIGEN_WORKAROUND_FOR_QT_BUG_CALLING_WRONG_OPERATOR_NEW
 
 #define EIGEN_MAKE_ALIGNED_OPERATOR_NEW EIGEN_MAKE_ALIGNED_OPERATOR_NEW_IF(true)
 #define EIGEN_MAKE_ALIGNED_OPERATOR_NEW_IF_VECTORIZABLE(Scalar,Size) \