UNSHIFT array-name , expression

   Synopsis:
      Adds a value to the beginning of an array

   Notes:
      This statement only works on one-dimensional arrays (stacks). If you use
         it with a multi-dimensional array, you'll get an error.

      Adds a new cell to the beinning of the array, containing the value of the
         expression. Doing so increases (for example) an array of ten values to
         an array of eleven.
      All Axbasic arrays have a maximum number of cells of 1,000,000. If the
         UNSHIFT statement exceeds this maximum, you will get an error.

   Compatibility:
      Since Axbasic v1.4

   Examples:
      DATA "foo", "bar", "baz"

      DIM stuff$ (3)
      FOR a = 1 TO 3
         READ stuff$ (a)
      NEXT a

      ! Add a new value
      UNSHIFT stuff$, "plugh"
      ! Display the new size of the array
      LET number = SIZE stuff$
      PRINT number
