Breakpoints are always re-set by the embedder after compilation, so we
don't want to store the corresponding breakpoint objects.
Also don't serialize WASM_INTERPRETER_ENTRY stubs as they are replaced
by ordinary WASM_FUNCTION code at instantiation anyway, and skip
WASM_TO_JS wrappers which are recompiled on each instantiation.
Instead, we serialize the Illegal builtin, and also use that one
instead of the placeholder when compiling the wasm code initially.

R=titzer@chromium.org, yangguo@chromium.org
BUG=v8:5822

Review-Url: https://codereview.chromium.org/2629853004
Cr-Commit-Position: refs/heads/master@{#42451}