Stablish rule for submodule procedures declaration compatible with older cmake versions

[jalvesz]

Motivation

I have had problems with this issue https://gitlab.kitware.com/cmake/cmake/-/issues/18427#note_983426 when compiling stdlib under systems with cmake 3.17.5 (which for several reasons can't be upgraded) and then having build errors with spurious modules.

I had to patch locally the procedures by replacing for instance module pure function by pure module function etc etc.

I would like to propose that module procedures are to be declared as:
<attribute> <attribute> module <function/subroutine> <name>
instead of
module <attribute> <attribute> <function/subroutine> <name>

This would ensure an easy retro compatibility.

Affected modules :
stdlib_system_subprocess
stdlib_system
stdlib_linalg_diag
stdlib_linalg

Prior Art

No response

Additional Information

No response

[jalvesz]

The public attribute is only allowed in the specification part of a module. There is no reason to add it, nor it will be accepted by the compiler(s) when declaring a procedure.

This issue only concerns the mix of the module attribute when defining procedures in submodules and other attributes such as the kind (real, integer, etc) or elemental, pure, etc.

[BhoomishGupta]

Okay, Thanks for clarifying.

[jalvesz]

closed after #1041 thanks @BhoomishGupta