#27370 breaks narrowing for constructor functions

[sandersn]

Based on code from uglify:

/** @constructor */
function AtTop(val) { this.val = val }
/** @type {*} */
var x = 1;
if (x instanceof AtTop) {
    x.val
}

Expected behavior:

x doesn't narrow inside the if and x: any and x.val: any.

Actual behavior:
x narrows to x: {} and gives an error on x.val.

I think the reason is that constructor functions are special-cased in resolveCallExpression -- they still only have call signatures, not construct signatures. The code in narrowTypeByInstanceof probably needs the same special-casing (or to have it in one place).