[es6] Make assignment to new.target an early ReferenceError

[es6] Make assignment to new.target an early ReferenceError

In doing so, fix calls CheckAndRewriteReferenceExpression to take proper
start and end positions (instead of just pointing at the first token in
the LHS expression).

BUG=v8:4370
LOG=n

Review URL: https://codereview.chromium.org/1290013002

Cr-Commit-Position: refs/heads/master@{#30166}