DateTimeOffsetFieldAccessor: Fixed size of value to 16

Author: alex-kulakov

Orm/Xtensive.Orm/Tuples/Packed/PackedFieldAccessor.cs

@@ -578,7 +578,11 @@ protected override void Encode(DateTimeOffset value, long[] values, int offset)
 
     private static unsafe int GetSize()
     {
-      return sizeof(DateTimeOffset);
+      // Depending on architecture, x86 or x64, the size of DateTimeOffset is either 12 or 16 respectively.
+      // Due to the fact that Rank calculation algorithm expects sizes to be equal to one of the power of two
+      // it returns wrong rank value for size 12 (bitsize = 96) which causes wrong choice of Encode/Decode methods.
+      // Setting it to 16 helps to solve Rank problem.
+      return sizeof(long) * 2;
     }
 
     public DateTimeOffsetFieldAccessor()