support destructuring for value specifications

Several times I’ve wanted to use destructuring when specifying values for existing declarations. It would be nice to support something like:

    String value1;
    String value2;
    [value1, value2] = ["x", "y"];

Use case 1: making specifications in different branches of a control structure, where currently you must:

    String value1;
    String value2;

    if (1==1) {
        value result = identity(["a", "b"]);
        value1 = result[0];
        value2 = result[0];
    }
    else {
        value result = identity(["c", "d"]);
        value1 = result[0];
        value2 = result[0];
    }

Use case 2: when you’d like to annotate the declarations:

    "documentation for value1"
    String value1;

    "documentation for value2"
    String value2;

    value result = identity(["a", "b"]);
    value1 = result[0];
    value2 = result[1];

[jvasileff]

oops… my first example has a bug. I guess that just helps make my point.

[luolong]

Variable values as well… Otherwise it seems kind of arbitrary…