enclose whole value with quote if space is included

If a space is included in parameter value, The whole value should be
quoted. Also quote in value should be escaped.

Linux:

    $ export FOO="1 2 3"
    $ echo $FOO
    1 2 3
    $ echo "$FOO"
    1 2 3

Windows:

    > set FOO="1 2 3"
    > echo %FOO%
    "1 2 3"
    > echo "%FOO%"
    ""1 2 3""

This difference would cause escape issue...