[gfortran] Add ACCESS="APPEND" to OPEN statement

[Tobias.Schlueter@Physik.Uni-Muenchen.DE]

Quoting François-Xavier Coudert <fxcoudert@gmail.com>:
> Attached patch fixes PR libfortran/24892: g77 allows the ACCESS
> keywork of the OPEN statement to have value "APPEND", which is the
> same as POSITION="APPEND". The patch adds this possibility for
> compatibility reasons, warning if the code was compiled with
> -pedantic, and refusing the cases of conflicting ACCESS and POSITION
> keywords.
>
> Tested on ppc-darwin, regtesting still going on.
>
> OK for mainline? OK for 4.0?

Yes for both, provided it passes testing.  A testcase would be in place, though.

- Tobi

:REVIEWMAIL: