Unnamed array index sets

Mosel 6 makes it possible to work with unnamed index sets in places where this was previously not possible, including in the definition of arrays that are used as fields in record structures. As a consequence of the revised set handling, a few cases where unnamed sets were already accepted in previous releases now behave in a more systematic way that is different from previous behaviour: unless two arrays specifically are declared to take the same (named) index, their sets are now always treated as being different, including for single line declarations of multiple arrays. As a result, code such as the following that works with previous versions of Mosel:

public declarations
  A,B: array(set of string) of integer
  data=`
data:[('a') [1 2] ('b') [3 4]]
`
end-declarations

initialisations from 'mmsystem.text:data'
  [A,B] as 'data'
end-initialisations

will fail with the error message "Incompatible types for 'initialisations'". The correction consists in adding a name for the set in the array declaration in order to make sure that both arrays have indeed the same index set:

public declarations
  A,B: array(S: set of string) of integer
end-declarations