xargs, arguments separator and escapes.

xargs uses blanks (not only newlines!) to split input line into arguments.
Though, there is some options, which turns this defailt off implicitly or
explicitly.

Here is summary:

    +--------+--------------------+---------------------+
    | Option | Argument separator | Escapes             |
    +--------+--------------------+---------------------+
    | -L     | blank              | Interpreted (work)  |
    +--------+--------------------+---------------------+
    | -d     | user defined       | Literal (not work)  | 
    +--------+--------------------+---------------------+
    | -I     | newline            | Interpreted (work)  |
    +--------+--------------------+---------------------+