xwayland: Allow for regular transport types for listen

Xwayland uses the command line option “-listen” to pass file descriptors from the Wayland compositor.

That breaks the traditional, documented behavior of the “-listen” command line option which is to enable a transport type.

Checks if the given option starts with a digit, otherwise treat it as a regular transport type.

Closes: #817 (closed) Suggested-by: Rodrigo Exterckötter Tjäder Signed-off-by: Olivier Fourdan ofourdan@redhat.com