Unary postfix fixes

tests/binaryen/block-stack.js

@@ -0,0 +1,19 @@
+var binaryen = require("binaryen");
+
+// "non-final block elements returning a value must be drop()ed"
+// "0 == 0: block with value must not have last element that is none, on"
+
+var mod = new binaryen.Module();
+
+var funcType = mod.addFunctionType("i", binaryen.i32, []);
+var func = mod.addFunction("test", funcType, [ binaryen.i32 ],
+  mod.block("", [
+    mod.teeLocal(0, mod.i32.const(1)),
+    mod.nop()
+  ], binaryen.i32)
+);
+mod.addExport("test", func);
+
+console.log(mod.emitText());
+if (!mod.validate())
+  console.log("-> does not validate");