Change default locale

Change the value of LC_ALL that should not be defined; only LANGUAGES and LANG
should be defined (see `info gettext' for more information).
Declare 'TRASH_DIR' into 'zshenv'

The 'TRASH_DIR' was both declared into 'zshenv' (with the name 'TRASH') and in
'rc/alias' (with the name 'TRASH_DIR'). The 'rm' alias was using 'TRASH_DIR'.
Fix all this mixed declaration by only one of 'TRASH_DIR' into 'zshenv'.