Error on left hand function reference

[Jerry DeLisle]

Hi all,

I spotted this today on the Fortran-Lang Discourse.

It would not be setting precednce for us to allow an extension and turn
this into a warning with -std=gnu and an error of strict compliance is
wanted.

https://fortran-lang.discourse.group/t/error-the-leftmost-part-ref-in-a-data-ref-cannot-be-a-function-reference/4990

I will create a PR and chase this one if concurrence here.

Opinions?

Jerry