implement chapter 11 in rust

lox/fibonacci.lox

@@ -0,0 +1,9 @@
+var a = 0;
+var temp;
+
+var b = 1;
+for(var b = 1; a < 1000; b = temp + b) {
+    print a;
+    temp = a;
+    a = b;
+}

lox/name_redefinition.lox

@@ -0,0 +1,4 @@
+fun bad() {
+  var a = "first";
+  var a = "second";
+}

lox/scoping.lox

@@ -0,0 +1,10 @@
+var a = "global";
+{
+  fun showA() {
+    print a;
+  }
+
+  showA();
+  var a = "block";
+  showA();
+}

lox/top_level_return.lox

@@ -0,0 +1 @@
+return "at top level";