Make try body start with 'do' (#2846)

In WebAssembly/exception-handling#52, We decided to put `try` bodies in
a `do` clause to be more consistent with `catch`.

- Before
```wast
(try
  ...
  (catch
    ...
  )
)
```

- After
```wast
(try
  (do
    ...
  )
  (catch
    ...
  )
)
```

Another upside of this change is when there are multiple instructions
within a `try` body, we no longer need to wrap them in a `block`.

1 files changed, 15 insertions, 5 deletions

diff --git a/test/reference-types.wast b/test/reference-types.wast
index 1c2602c24..b5c1f9c41 100644
--- a/test/reference-types.wast
+++ b/test/reference-types.wast
@@ -202,7 +202,9 @@
     ;; Test subtype relationship for try return type
     (drop
       (try (result anyref)
-        (local.get $local_anyref)
+        (do
+          (local.get $local_anyref)
+        )
         (catch
           (exnref.pop)
         )
@@ -210,7 +212,9 @@
     )
     (drop
       (try (result anyref)
-        (ref.func $foo)
+        (do
+          (ref.func $foo)
+        )
         (catch
           (drop (exnref.pop))
           (ref.null)
@@ -219,7 +223,9 @@
     )
     (drop
       (try (result funcref)
-        (ref.func $foo)
+        (do
+          (ref.func $foo)
+        )
         (catch
           (drop (exnref.pop))
           (ref.null)
@@ -228,7 +234,9 @@
     )
     (drop
       (try (result exnref)
-        (ref.null)
+        (do
+          (ref.null)
+        )
         (catch
           (exnref.pop)
         )
@@ -236,7 +244,9 @@
     )
     (drop
       (try (result nullref)
-        (ref.null)
+        (do
+          (ref.null)
+        )
         (catch
           (drop (exnref.pop))
           (ref.null)