Dear all,

In the spirit of c/c++ using the .i/.ii extensions for intermediates,
use the .fi/.fii intermediate extensions for gfortran fixed/free form
sources when -save-temps is invoked to avoid various issues.

The documentation part will be submitted separately, because it
involves adding a "Developer options" mini-section (as suggested by
Harald) and moving the -fdump-* options from "Options for debugging
your program or GNU Fortran" section.

Regards,
Rimvydas