XiSys will now control all system related variables (so far only stdout).

Also added "<=" operator, which can be used to set the (setable)
attributes of any data type. This can be used on the new sys variable
from the new sys module as follows:

    import sys
    <= sys 'stdout' => file "test.txt" 'plain_writer'

This will redirect all standard output to a file named test.txt.