[INTERPRETER]
* NEW: String value can be used like object.
* NEW: String[X] returns the X-th character of the string, 0 being the first one.
* NEW: String[X, N] returns N characters from the position X, 0 being the first one. IF N is strictly negative, then all characters from the position X, except the last N characters are returned.
* NEW: String.Len returns the length of the string.

[COMPILER]
* NEW: Allow the [] operator to be applied to a string.