Add Array.prototype.filter polyfill.

This is currently required (and only used by) the
composable-computed-properties feature. If that feature is enabled it
will not work in non-ES5 browsers (specifically it is not available in
IE8 and lower).
Merge pull request #4213 from rjackson/bring-back-array-filter-polyfil

Add Array.prototype.filter polyfill.