Add filter option to the ls

[Duca]

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.