This is needed for the asm.js -> WASM pipeline. A single exported
function is exported as __single_function__, but we still want to see
the correct function name on the stack, so the underlying wasm function
has to carry the original name.

R=ahaas@chromium.org, titzer@chromium.org
BUG=v8:4203

Review-Url: https://codereview.chromium.org/2406133003
Cr-Commit-Position: refs/heads/master@{#40159}