2.18.2 Stuff:

- Fix handling of AlwaysLoginCurrentSession and DoubleLoginWarning so
 it works for the non-migratable case (for Xnest, XDMCP, etc.).  Fixes
 bug #172600.
- Use an unsigned char buffer in gdm_fdgetc (Brian Cameron)
- Just display the default "authentication failed" message when we
 receive PAM_AUTHINFO_UNAVAIL (Lo\357c Minier)
- Fix for bug #428630. (Brian Cameron)
- Translation updates (Peter Bach, Funda Wang, Pema Geyleg, Christophe Merlet,
 St�phane Raimbault, Priit Laes)