use gc interface directly, document

tests/binaryen/break-value.js

@@ -0,0 +1,24 @@
+var binaryen = require("binaryen");
+
+var mod = new binaryen.Module();
+var ftype = mod.addFunctionType("ii", binaryen.i32, [ binaryen.i32 ]);
+mod.addFunction("test", ftype, [],
+  mod.block("label", [
+    mod.drop( // "br_if returns the value too"
+      mod.break("label",
+        // condition: $0 == 1
+        mod.i32.eq(
+          mod.getLocal(0, binaryen.i32),
+          mod.i32.const(1)
+        ),
+        // value: 1
+        mod.i32.const(1)
+      )
+    ),
+    // push: 0
+    mod.i32.const(0)
+  ], binaryen.i32)
+);
+console.log(mod.emitText());
+
+mod.validate();