(Towards #2586) Add support for object-oriented `var =[>] this[%...]%procedure(...)` assignment

[JulienRemy]

Currently pointer assignments of the form var =[>] this[%...]%procedure(...) are CodeBlocks wrapping fparser Function_Reference objects. This converts them to assignments with a call on the rhs.

Notes:

• a workaround was required to deal with some fparser Intrinsic_Function_Reference, wrongly parsed as Function_Reference fparser/#447 and associated TODO comments.
• this does not deal with the Structure_Constructor case mentioned here so it does not close #2586.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 99.86%. Comparing base (d92f13f) to head (b974455).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #2649 +/- ## ======================================= Coverage 99.86% 99.86% ======================================= Files 352 352 Lines 48507 48509 +2 ======================================= + Hits 48442 48444 +2 Misses 65 65 ```

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[arporter]

Hi @JulienRemy, I can't remember what you said about PRs on Monday. Was this the one that's ready for a review?

[JulienRemy]

Hi @arporter, this one is indeed ready to review when you have time for this.

[arporter]

Integration tests were green.