This patch changes the parser to allow for-of initializer
var-redeclaration of non-destructured catch parameters.

Previously, the spec allowed var-redeclaration of a
non-destructured catch parameter…

    try {} catch (e) { var e; }

…except in the particular case where the var declaration is
a for-of initializer:

    try {} catch (e) { for (var e of whatever) {} }

https://github.com/tc39/ecma262/pull/1393 removes this strange
exceptional case. This patch implements that change.

BUG=v8:8759

Change-Id: Ia4e33ac1eab89085f8a5fdb547f479cfa38bbee5
Reviewed-on: https://chromium-review.googlesource.com/c/1444954Reviewed-by: Toon Verwaest <verwaest@chromium.org>
Commit-Queue: Mathias Bynens <mathias@chromium.org>
Cr-Commit-Position: refs/heads/master@{#59209}