Correct Extent constructor to be unambiguous.
ExecutionObject unit test needs to use int instead of dax::Id

With 64bit ids the ExecutionObject unit test signature would
be wrong, as we are expect int return type and first parameter.
To look up exec field values you need to use IJKIndex or dax::Id

In this case we had been using an int, which only worked correctly
since under 32bit mode dax::Id equals int.
Merge branch 'Support64BitIds'