switch off backwards compatibility with compiler arguments

[Leonard-Reuter]

It would be great to be able to switch off backwards compatibility 'features' with compiler arguments:
eg.:
-implicit=none
-case_sensitive=true
to enforce good code for new projects.

[milancurcic]

Most compilers implement non-standard features like this. This repo is for proposals to the Fortran Standard Committee.

[certik]

Most compilers implement non-standard features like this. This repo is for proposals to the Fortran Standard Committee.

I think we allow to discuss issues more broadly here, and I think all these overlap:

• The standard itself
• What compilers do
• What the community does

This issue is related to the discussions at #40, #83.