The bug was about instantiating a module with elements segment being out-of-bounds, however, it was with zero length. E.g.:
```
(module
(table 0 anyfunc)
(elem (i32.const 1))
)
```
In our impl there was no out-of-bounds, because there was no attempt to set any table entry.
This change adds early check for specifically this case.
Move all spec testsuite into `/tests` directory.
So it means that several changes will happen:
- Compilation will share common dependencies in target directory. This should make CI builds faster. This also should reduce space requirements.
- Common Cargo.lock file
- `cargo test` will include spec tests.
- `cargo check --tests` will also include spec tests.
Sergey Pepyakin