Timeout for testing out different browser

When xdg-open uses open_generic it tries out different browsers by simply checking if the previous execution failed. usually this is fine, but what I find annoying is, that it also happens when I for some reason kill the web-browser at some point. E.g. it opens firefox and after a day (i.e. I ssh into my computer and need to free some memory - so I kill firefox) I kill it -then xdg-open assumes that firefox is not the right application and tries the next possible browser.

I would prefer if a form of time out exists. Meaning if the application tried crashed after e.g. more then 60 seconds don't assume it failed to pick the right application but accept that an actual crash of some kind happened.

Based off original patch from Lutz Fischer

Fixes: #190