Redefined "$" to mean sort.

Removed "csort" and instead made "$" have two arguments by default. Of
course, just one can still be provided via the stop syntax:

    l = ["5", "42", "320", "16"]
    println $ list l;
    println $ list l int`

outputs:

    [16, 320, 42, 5]
    [5, 16, 42, 320]

To obtain the old behavior of "$", the "+:" operator can be used.
Specifically:

    $ somelist

is now

    +: somelist;
Fixed hashing bug
Cleaned up variable storage in XiEnvironment.