Add bash shebang to files

Signed-off-by: Severin Kaderli <severin.kaderli@gmail.com>

system/.bash_logout

@@ -1,3 +1,4 @@
+#!/bin/bash
 # ~/.bash_logout: executed by bash(1) when login shell exits.
 
 # when leaving the console clear the screen to increase privacy

system/.xinitrc

@@ -1,3 +1,4 @@
+#!/bin/bash
 # Disable screen saver
 xset s off
 xset -dpms

system/.xprofile

@@ -1,3 +1,4 @@
+#!/bin/bash
 # Disable screen saver
 xset s off
 xset -dpms