The new object will hold information which is shared by all clones of a
WasmCompiledModule, e.g. the decoded asm.js offset table, and in the
future also breakpoints. From there, we can set them on each new
instantiation of any clone.

While already changing lots of the code base, I also renamed all
getters from "get_foo" to "foo", to conform to the style guide.

R=titzer@chromium.org, yangguo@chromium.org
BUG=v8:5732

Review-Url: https://codereview.chromium.org/2591653002
Cr-Commit-Position: refs/heads/master@{#41862}