[flang] Merge pull request flang-compiler/f18#553 from flang-compiler/pmk-fixes

Support "*length" character length specifier on declarations, plus a couple small fixes.

Original-commit: flang-compiler/f18@afe12f7f4b36ad3c1f798a658f1febcfd7eb1caf
Reviewed-on: https://github.com/flang-compiler/f18/pull/553