This changes the interface descriptor for the arguments adaptor to also
contain an explicit register for the new.target value. Note that the
stub still clobbers the register for now.

This is a preparatory CL to allows us passing new.target in a register
instead of via a side-channel through the construct stub frame.

R=bmeurer@chromium.org
BUG=v8:4544
LOG=n

Review URL: https://codereview.chromium.org/1457313002

Cr-Commit-Position: refs/heads/master@{#32117}