Create these new files in flang/lib/Semantics:
openmp-utils.cpp/.h - Common utilities
check-omp-atomic.cpp - Atomic-related checks
check-omp-loop.cpp - Loop constructs/clauses
check-omp-metadirective.cpp - Metadirective-related checks
Update lists of included headers, std in particular.
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Co-authored-by: Jack Styles <jack.styles@arm.com>