Restore the previous behaviour concerning executable extensions on windows

[Ralf Habacker]

Fridrich Strba schrieb:
> This patch restores the behaviour that existed before
> http://cgit.freedesktop.org/dbus/dbus/diff/dbus/dbus-spawn-win.c?id=6e214b5b3c283798b5743b4ebf7c9ec466fe3667 on windows. When the service file had a value of exec that was something like /some/path/filename, dbus was able to interpret it also as /some/path/filename.exe if that file existed.
>
>   
patch committed

Regards
 Ralf