[reference] Use xdg-open instead of firefox

[iacore]

When I used ide7, I noticed it's not showing anything. I tried to fix opening browser on Linux, but I don't know Seed7 enough.

On Linux, opening browser should be like this:

• use xdg-open http://example.com/ (free desktop)
• run $BROWSER http://example.com/ if env var BROWSER exist
• hardcoded browser paths

Also, I noticed this function will not fail if non of the browser exist (browser.program is empty).

[Wolf-SO]

To my knowledge, xdg-open is the

[...] command in the Linux system is used to open a file or URL in the user’s preferred application.

And this command is part of the xdg-utils package. So we must check first if this package is installed. Also, we need to get the result of the startProcess to be stored in browser.program while your (@iacore ) cmd_sh only does part of this task.

If this package is installed, we can get the default web browser like this:

xdg-settings get default-web-browser