Make sure to check that the number of declared functions (specified in the
function section) matches the number of function bodies, even if the code
section is omitted.

Note that it is valid to have a function section with zero declared functions
and an omitted code section, and vice versa.

Bug: v8:8514
Change-Id: I4effa5abe2ed6d71146a665d2df6a2f48b5a84be
Reviewed-on: https://chromium-review.googlesource.com/c/1351306
Commit-Queue: Ben Smith <binji@chromium.org>
Reviewed-by: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#57949}