Throw errors in strict mode for octal strings

Adds a directive tracker for the parser/tokenizer to
allow parsing depending on directive context.

test/mocha/directives.js

@@ -0,0 +1,61 @@
+var assert = require("assert");
+var uglify = require("../../");
+
+describe("Directives", function() {
+    it ("Should allow tokenizer to store directives state", function() {
+        var tokenizer = uglify.tokenizer("", "foo.js");
+
+        // Stack level 0
+        assert.strictEqual(tokenizer.has_directive("use strict"), false);
+        assert.strictEqual(tokenizer.has_directive("use asm"), false);
+        assert.strictEqual(tokenizer.has_directive("use thing"), false);
+
+        // Stack level 2
+        tokenizer.push_directives_stack();
+        tokenizer.push_directives_stack();
+        tokenizer.add_directive("use strict");
+        assert.strictEqual(tokenizer.has_directive("use strict"), true);
+        assert.strictEqual(tokenizer.has_directive("use asm"), false);
+        assert.strictEqual(tokenizer.has_directive("use thing"), false);
+
+        // Stack level 3
+        tokenizer.push_directives_stack();
+        tokenizer.add_directive("use strict");
+        tokenizer.add_directive("use asm");
+        assert.strictEqual(tokenizer.has_directive("use strict"), true);
+        assert.strictEqual(tokenizer.has_directive("use asm"), true);
+        assert.strictEqual(tokenizer.has_directive("use thing"), false);
+
+        // Stack level 2
+        tokenizer.pop_directives_stack();
+        assert.strictEqual(tokenizer.has_directive("use strict"), true);
+        assert.strictEqual(tokenizer.has_directive("use asm"), false);
+        assert.strictEqual(tokenizer.has_directive("use thing"), false);
+
+        // Stack level 3
+        tokenizer.push_directives_stack();
+        tokenizer.add_directive("use thing");
+        tokenizer.add_directive("use\\\nasm");
+        assert.strictEqual(tokenizer.has_directive("use strict"), true);
+        assert.strictEqual(tokenizer.has_directive("use asm"), false); // Directives are strict!
+        assert.strictEqual(tokenizer.has_directive("use thing"), true);
+
+        // Stack level 2
+        tokenizer.pop_directives_stack();
+        assert.strictEqual(tokenizer.has_directive("use strict"), true);
+        assert.strictEqual(tokenizer.has_directive("use asm"), false);
+        assert.strictEqual(tokenizer.has_directive("use thing"), false);
+
+        // Stack level 1
+        tokenizer.pop_directives_stack();
+        assert.strictEqual(tokenizer.has_directive("use strict"), false);
+        assert.strictEqual(tokenizer.has_directive("use asm"), false);
+        assert.strictEqual(tokenizer.has_directive("use thing"), false);
+
+        // Stack level 0
+        tokenizer.pop_directives_stack();
+        assert.strictEqual(tokenizer.has_directive("use strict"), false);
+        assert.strictEqual(tokenizer.has_directive("use asm"), false);
+        assert.strictEqual(tokenizer.has_directive("use thing"), false);
+    });
+});