Xrdp needs to know the current display name (for setting up it's
own server sockets accordingly). Instead of exporting an internal
field, adding a little getter for this.
Signed-off-by: Enrico Weigelt, metux IT consult <info@metux.net>
Part-of: <https://gitlab.freedesktop.org/xorg/xserver/-/merge_requests/1783>
Enrico Weigelt, metux IT consult