[flang] Merge pull request flang-compiler/f18#614 from flang-compiler/tsk-generics

 Improve handling of generics with same name as type or procedure

Original-commit: flang-compiler/f18@a1e26df148c4d480178aa8b765aad4ceaaa5eae2
Reviewed-on: https://github.com/flang-compiler/f18/pull/614