bug#20172: make each ls sort option say what is first on the man page

[積丹尼 Dan Jacobson]

Please make
$ man ls|grep -e -[St].*sort
       -S     sort by file size
       -t     sort by modification time, newest first
say
$ man ls|grep -e -[St].*sort
       -S     sort by file size, largest first
       -t     sort by modification time, newest first
even though yes, documented elsewhere.
There may be others too...