This patch updates internal data structures used by V8 to support
multiple indirect function tables (WebAssembly/design#682). But, since
this feature is post-MVP, the functionality is not directly exposed and
parsing/generation of WebAssembly is left unchanged. Nevertheless, it
is being used in an experiment to implement fine-grained control flow
integrity based on C/C++ types.

BUG=

Review-Url: https://codereview.chromium.org/2174123002
Cr-Commit-Position: refs/heads/master@{#38110}