[wwwdocs][Fortran] gcc-10/porting_to.html – Fortran's argument-checking

[Tobias Burnus]

As I assume that Wilco's -fno-common porting-to patch will be submitted 
first, I didn't include the full boilerplate; cf. 
https://gcc.gnu.org/ml/gcc-patches/2019-11/msg02662.html

As suggested by Eric, an entry in porting-to about the Fortran 
argument-checking change could also be useful, cf. 
https://gcc.gnu.org/ml/gcc-patches/2019-11/msg02711.html

Hence: How about the following?

Tobias