[TurboFan] Incorrect typing of String.lastIndexOf JSCall nodes

JSCall nodes to builtins kStringLastIndexOf and kStringIndexOf are incorrectly typed;

This bug has been found by @_tsuro .

This repository contains a trigger with an explanation of the bug as well as a full exploit.

It is associated to a future doar-e.github.com article.

Name		Name	Last commit message	Last commit date
Latest commit History 16 Commits
step0		step0
step1		step1
step2		step2
trigger		trigger
README.md		README.md
exploit.js		exploit.js
pwn_stringLastIndexOf.gif		pwn_stringLastIndexOf.gif
wasm.js		wasm.js

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