Assume that malloc returns memory that is 16 byte-aligned

This fixes an issue with inconsistent memory allocation/deallocation of
MeshPoint in Python.

libsrc/general/mysimd.hpp

@@ -60,12 +60,30 @@ namespace netgen
   template <typename T>
   class AlignedAlloc
   {
+    protected:
+      static void * aligned_malloc(size_t s)
+      {
+        // Assume 16 byte alignment of standard library
+        if(alignof(T)<=16)
+            return malloc(s);
+        else
+            return  _mm_malloc(s, alignof(T));
+      }
+
+      static void aligned_free(void *p)
+      {
+        if(alignof(T)<=16)
+            free(p);
+        else
+            _mm_free(p);
+      }
+
   public:
     void * operator new (size_t s, void *p) { return p; }
-    void * operator new (size_t s) { return  _mm_malloc(s, alignof(T)); }
-    void * operator new[] (size_t s) { return  _mm_malloc(s, alignof(T)); }
-    void operator delete (void * p) { _mm_free(p); }
-    void operator delete[] (void * p) { _mm_free(p); }
+    void * operator new (size_t s) { return aligned_malloc(s); }
+    void * operator new[] (size_t s) { return aligned_malloc(s); }
+    void operator delete (void * p) { aligned_free(p); }
+    void operator delete[] (void * p) { aligned_free(p); }
   };
   
   template<>