Bug#898317: xdg-open: Argument injection in xdg-open open_envvar

[Salvatore Bonaccorso]

Control: found -1 1.1.0~rc1+git20111210-7.4

The issue seems present as well in earlier version, though in upstream
commit 3c2fe9f1ebbfdbffcc9e38a767641805cec3340b this part was
refactored.