Allow out of line functions to use inline dataset operations

It should be possible to have something like

myFunc(dataset(rec) x, string y ) := DEFINE count(x(value = y));

To common up mutliple calls to the same function - e.g., see getValue() in klogemann58.eclxml

At the moment it generates a thor graph, which is not going to work in the majority of cases.  Avoiding spotting the thor boundaries should fix that, but breaks other existing (werid) examples.