Add filter option to the ls

hi, i've work to the ls because i've needed, for a script, to have only the subdirectory, i can use ls | sed (and i 
do this), but i've think that if ls could support a simple level of to filtering then it could be more usable.

The patch refer to the current version of fileutils that's on the ftp site, it's the 4.1.

The patch is very simple, for check if a file must be to print to the screen or not, it do only two operations: a 
<< and a &&.

my patch is very poor of comment because the code is very simple.