OpenACC data clause operations previously required that the variable
operand implemented PointerLikeType interface. This was a reasonable
constraint because the dialects currently mixed with `acc` do use
pointers to represent variables. However, this forces the "pointer"
abstraction to be exposed too early and some cases are not cleanly
representable through this approach (more specifically FIR's `fix.box`
abstraction).
Thus, relax this by allowing a variable to be a type which implements
either `PointerLikeType` interface or `MappableType` interface.
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