Sync up with wabt latest modification (#296) (#786)

- Remove "--enable-reference-types" and "--enable-bulk-memory" for wat2wasm
to support finished proposals.

- Ignore invalid module in the thread spec repo:
``` wast
;; my_elem.wast
(module
  (table $t 10 funcref)
  (func $f)
  (elem $t (i32.const 0) 0)
  (elem $t (i32.const 0) $f $f)
  (elem $t (offset (i32.const 0)) $f $f)
)
```

run with reference interpreter under spec/interpreter:
``` shell
$ ./wasm ../../../my_elem.wast
../../../my_elem.wast:5.9-5.11: syntax error: duplicate elem segment $t
```

- use a specific commit instead of the latest commit on the thread spec repo

tests/wamr-test-suites/test_wamr.sh

@@ -290,7 +290,8 @@ function spec_test()
 
         # fetch spec for threads proposal
         git fetch threads
-        git reset --hard HEAD
+        # [interpreter] Threading (#179) Fri Aug 6 18:02:59 2021 +0200
+        git reset --hard 0d115b494d640eb0c1c352941fd14ca0bad926d3
         git checkout threads/main
 
         git apply ../../spec-test-script/thread_proposal_ignore_cases.patch