[Fortran, OpenACC] Reject vars of different scope in $acc declare (PR94120)

[Tobias Burnus]

[This fixes a bunch of issues found when actually only
wanting to add a check for the following restriction.]

OpenACC's "Declare Directive" has the following restriction:

"A declare directive must be in the same scope
  as the declaration of any var that appears in
  the data clauses of the directive."

The gfortran now rejects a "var" declared is in a different
namespace than the "$acc declare". (Use-associated variables
are already rejected.) Testing showed that a straight-forward
check fails if the result variable is the function name – as
then the function symbol is in the parent scope. — Extending
the failing test to use a result variable showed that the
current is-a-module-variable check didn't work and when fixing,
one was running into a likewise issue.

The reason that I exclude 's' being a module is that at
resolution time, an is-variable check is done.


The other changes are because the following restriction was
mishandled:

"In a Fortran module declaration section, only
  create, copyin, device_resident, and link clauses are allowed."

But all examples where for variables using those in a module
procedure …


OK for the trunk?

Cheers,

Tobias

PS: For those who wounder what happens in a BLOCK DATA construct:
gfortran outrightly rejects 'acc declare'. (It probably should
work for COMMON blocks with 'declare device_resident' – but
currently the spec only permits it in program/subroutine/function
+ declaration part of a module.)

PPS: The PR shows (for C) that one can construct a test case,
which violates the OpenACC restriction and actually fails with
an ICE. I have a draft patch for C (see PR) but not yet one for
C++, hence, I start with the Fortran side. – I currently still
struggle to write a same-scope check in C++.
[The C test case in turn was a fallout of debugging an
ICE-on-valid-code issue …]

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