gdm should have option for per-host .xsession-errors file

Submitted by David Biesack

Description

For those of us who have a shared network home directory, logging onto two machines causes them to stomp on the same .xsession-errors file. (However, I want to reuse most of the rest of my X config, i.e. ~/.config). Thus, it would be nice to have a per-host .xsession-errors file or some other way to configure the .xsession-errors file location.

See also https://bugs.launchpad.net/ubuntu/+source/gdm/+bug/382879 which shows how editing /etc/X11/Xsession (or /etc/gdm/Xsession) allows configuring the error file ERRFILE. gdm should have some similar capability