[flang] Simplify proc-component-ref and variable parsing, do not try to...

[flang] Simplify proc-component-ref and variable parsing, do not try to support function calls via components of function results.

Original-commit: flang-compiler/f18@05886ddb80e31f3caec96cbaba1fea274db7c61a
Reviewed-on: https://github.com/flang-compiler/f18/pull/56
Tree-same-pre-rewrite: false