The function name table will now always be set; a CHECK will fail if
the length would exceed the integer range.
Also, the resolution of undefined function names to "<WASM UNNAMED>" is
moved over to the wasm side.

R=titzer@chromium.org

Review-Url: https://codereview.chromium.org/2057523002
Cr-Commit-Position: refs/heads/master@{#36918}