Even though a previous patch made the number of slots pushed/claimed on
the stack aligned, the boundary between frames was not a multiple of
two slots as well. We were pushing the number of arguments (which belongs
in the stub's frame) together with the arguments to pass to the
constructor function (which belong to the frame of the constructor
function). Those need to be separated so we can drop the arguments without
messing up the alignment.

Bug: v8:6644
Change-Id: I839a4ab9caf451623fbcf03dd8a8afe5879fef99
Reviewed-on: https://chromium-review.googlesource.com/771670Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
Commit-Queue: Georgia Kouveli <georgia.kouveli@arm.com>
Cr-Commit-Position: refs/heads/master@{#49391}