fix default locale and remove direct declaration of dependence

[wcbing]

remove direct declaration of dependence

don't need direct declare

pulseaudio -> pulseaudio-utils
xfce4 -> xfce4-session -> x11-xserver-utils
xfce4 -> xfce4-pulseaudio-plugin

default locale

Although locale-gen and declaring env, but default is still C.UTF-8

$ echo $LANG
C.UTF-8
$ cat /etc/default/locale
LANG=C.UTF-8
$ locale
LANG=C.UTF-8
LANGUAGE=
LC_CTYPE="C.UTF-8"
LC_NUMERIC="C.UTF-8"
...