OpenACC 3.2 allowed the wait clause to the data construct. This patch
adds a unit attribute and a variadic operand to the data operation to model
the wait clause in a similar way it was added to other data operation.
The attribute models the presence of the clause without any argument. When
arguments are provided they are placed in the wait operand.
Depends on D154111
Reviewed By: razvanlupusoru
Differential Revision: https://reviews.llvm.org/D154131
61807f5c29