OpenACC in Flang

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Intentional deviation from the specification

The end directive for combined construct can omit the loop keyword.
An !$acc routine with no parallelism clause is treated as if the seq clause was present.
!$acc end loop does not trigger a parsing error and is just ignored.
The restriction on !$acc data required clauses is emitted as a portability warning instead of an error as other compiler accepts it.
The if clause accepts scalar integer expression in addition to scalar logical expression.
!$acc routine directive can be placed at the top level.
!$acc cache directive accepts scalar variable.