[flang] Merge pull request flang-compiler/f18#311 from flang-compiler/pmk-struct-checks

More structure constructor semantics checking

Original-commit: flang-compiler/f18@5561c9012c07c21cd043b0b0b8b2a03d6e42bebe
Reviewed-on: https://github.com/flang-compiler/f18/pull/311