The spec defines that indirect calls in WebAssembly code should cause a
validation error if no function table exists.

The CL contains the following changes:
1) Throw a validation error for indirect calls if the function table
   not exist.
2) Do not create TF nodes to throw a runtime error for indirect calls
   if the function table does not exist.
3) Fix existing unit tests by creating a dummy function table.
4) Add new a new test which tests that indirect calls without function
   table cause a validation error.

R=rossberg@chromium.org
CC=titzer@chromium.org

TEST=unittests/AstDecoderTest.IndirectCallsWithoutTableCrash

Review-Url: https://codereview.chromium.org/2484623002
Cr-Commit-Position: refs/heads/master@{#40802}