Create Dim_Screen.sh

This small shell script, will actually dim your screen even if your function keys are not working. (typically, people will still see the sun icon, with the slider moving side to side) but the screen will not dim! This patch fixes that problem. Tested working on an Acer Aspire One D270, and Debian 7 Wheezy. 

This patch also works, even if acpi_backlight=vendor and acpi_os=Linux grub settings do not!