promote ascii functions to elemental

[jalvesz]

Promote ascii functions from pure to elemental for potentially better optimization and ease use for array expressions manipulation.

[perazz]

I believe I remember that some older versions of gfortran had issues with elemental functions and character . However, that seems not an issue here as all tests pass with all supported gfortran versions. LGTM, thank you @jalvesz

[jalvesz]

Do you remember if it was a compile-time problem or a run-time problem? maybe it would be better to add array-like tests also ? I don't recall running into such problems.

[perazz]

I can't find a link right now in my bugzilla - I suggest we wait for another while, and if no further comments arise, this PR can be merged imho.

[jvdp1]

Thank you @perazz . I guess that the specs should be updated too.
Re: the history, I don't remember any specific reasons why they were not defined as elemental. These procedures were some of the first to be implemented in stdlib and the structure was not well defined yet (see e.g., #32 ).