This means command line parsing stops when it encounters the first
nonoption argument.
The result is that one no longer need to use '--' to ensure arguments
are passed to the shell/command, instead of parsed by foot.
That is, instead of
foot -- sh -c true
one can now do
foot sh -c true
Arguments to foot *must* go before the command:
foot --fullscreen sh -c true
We now create a copy of the config for each client, and updates it
with the values passed from the client.
Since we're not actually cloning it (and e.g. strdup() all strings
etc) we can't call conf_destroy() to free it, but need to free just
the strings we've replaced.
