Add gas test confirming that br instructions do not end blocks.

tests/diff.rs

@@ -122,4 +122,5 @@ mod gas {
 	def_gas_test!(simple);
 	def_gas_test!(start);
 	def_gas_test!(call);
+	def_gas_test!(branch);
 }

tests/expectations/gas/branch.wat

@@ -0,0 +1,29 @@
+(module
+  (type (;0;) (func (result i32)))
+  (type (;1;) (func (param i32)))
+  (import "env" "gas" (func (;0;) (type 1)))
+  (func (;1;) (type 0) (result i32)
+    (local i32 i32)
+    i32.const 3
+    call 0
+    block  ;; label = @1
+      i32.const 17
+      call 0
+      i32.const 0
+      set_local 0
+      i32.const 1
+      set_local 1
+      get_local 0
+      get_local 1
+      tee_local 0
+      i32.add
+      set_local 1
+      i32.const 1
+      br_if 0 (;@1;)
+      get_local 0
+      get_local 1
+      tee_local 0
+      i32.add
+      set_local 1
+    end
+    get_local 1))

tests/fixtures/gas/branch.wat

@@ -0,0 +1,27 @@
+(module
+	(func $fibonacci_with_break (result i32)
+		(local $x i32) (local $y i32)
+
+		(block $unrolled_loop
+			(set_local $x (i32.const 0))
+			(set_local $y (i32.const 1))
+
+			get_local $x
+			get_local $y
+			tee_local $x
+			i32.add
+			set_local $y
+
+			i32.const 1
+			br_if $unrolled_loop
+
+			get_local $x
+			get_local $y
+			tee_local $x
+			i32.add
+			set_local $y
+		)
+
+		get_local $y
+	)
+)

tests/fixtures/gas/call.wat

@@ -2,7 +2,6 @@
 	(func $add_locals (param $x i32) (param $y i32) (result i32)
 		(local $t i32)
 
-		;; This looks 
 		get_local $x
 		get_local $y
 		call $add

tests/fixtures/gas/ifs.wat

@@ -2,8 +2,8 @@
 	(func (param $x i32) (result i32)
 		(if (result i32)
 			(i32.const 1)
-			(i32.add (get_local $x) (i32.const 1))
-			(i32.popcnt (get_local $x))
+			(then (i32.add (get_local $x) (i32.const 1)))
+			(else (i32.popcnt (get_local $x)))
 		)
 	)
 )

tests/fixtures/gas/simple.wat

@@ -1,12 +1,14 @@
 (module
 	(func (export "simple")
 		(if (i32.const 1)
+			(then
 				(loop
 					i32.const 123
 					drop
 				)
 			)
 		)
+	)
 
 	(func
 		block