Installer should set defaults for locale, even if user doesn't change anything

[ericonr]

The installer defaults to enabling the en_US.UTF-8 locale (for glibc), but it leaves LANG= in /etc/locale.conf, instead of setting at least some value, if the user doesn't go into the locale dialog in the installer. This can lead to issues in some brittle environments: for example a Cinnamon local install won't be able to launch gnome-terminal.

This is easy to fix locally from a tty, but the installer shouldn't leave LANG empty by default. Let the people have UTF-8 :D