Super Constructor Calls need to use a vector slot, not an ic slot.

The Ast Call node is accustomed to using a vector IC slot for the
cases when it uses a CallIC. The super constructor work alters this
somewhat by using a CallConstructStub instead, however the
CallConstructStub expects a vector slot and not a vector ic slot.
This distinction needs to be maintained because slots and ic slots
have different clearing strategies and are handled differently.

R=dslomov@chromium.org
BUG=
LOG=N

Review URL: https://codereview.chromium.org/892113002

Cr-Commit-Position: refs/heads/master@{#26414}