Align the claimed arguments in Generate_JSConstructStubGeneric by pushing an
extra copy of the receiver as padding.

Bug: v8:6644
Change-Id: I77e92624ff32c21c8f3f310176aa2576c756b56c
Reviewed-on: https://chromium-review.googlesource.com/757098
Commit-Queue: Martyn Capewell <martyn.capewell@arm.com>
Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#49275}