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, 14 insertions, 6 deletions

diff --git a/test/exception-handling.wast.fromBinary.noDebugInfo b/test/exception-handling.wast.fromBinary.noDebugInfo
index 2c6f83c4d..97bda57c4 100644
--- a/test/exception-handling.wast.fromBinary.noDebugInfo
+++ b/test/exception-handling.wast.fromBinary.noDebugInfo
@@ -17,8 +17,10 @@
  (func $3
   (local $0 exnref)
   (try
-   (throw $event$0
-    (i32.const 0)
+   (do
+    (throw $event$0
+     (i32.const 0)
+    )
    )
    (catch
     (local.set $0
@@ -37,7 +39,9 @@
   )
   (block $label$4
    (try
-    (br $label$4)
+    (do
+     (br $label$4)
+    )
     (catch
      (drop
       (exnref.pop)
@@ -47,7 +51,9 @@
    )
   )
   (try
-   (nop)
+   (do
+    (nop)
+   )
    (catch
     (drop
      (exnref.pop)
@@ -55,7 +61,7 @@
    )
   )
   (try
-   (block
+   (do
     (call $1)
     (call $2)
    )
@@ -70,7 +76,9 @@
  )
  (func $4
   (try
-   (nop)
+   (do
+    (nop)
+   )
    (catch
     (drop
      (exnref.pop)