[wwwdocs][patch] gcc-15/changes.html: Fortran - mention F2023 logical-kind additions

[Tobias Burnus]

Let's make https://gcc.gnu.org/gcc-15/changes.html a bit more useful … 
While there were several useful Fortran commits already, only one seems 
to be about a new feature.

Thus, document selected_logical_kind and the ISO_FORTRAN_ENV additions.
Comments or suggestions before I commit it?

Tobias
Title: GCC 15 Release Series — Changes, New Features, and Fixes








GCC 15 Release SeriesChanges, New Features, and Fixes


This page is a "brief" summary of some of the huge number of improvements
in GCC 15.



Note: GCC 15 has not been released yet, so this document is
a work-in-progress.


Caveats

  ...




General Improvements


New Languages and Language specific improvements










Fortran


  Fortran 2023: The selected_logical_kind intrinsic function
      and, in the ISO_FORTRAN_ENV module, the named constants
      logical{8,16,32,64} and real16 were added.








New Targets and Target Specific Improvements








































Operating Systems



























Other significant improvements