fix & improve coverage of estree (#1935)

- fix `estree` conversion of getter/setter
- fix non-directive literal in `to_mozilla_ast()`
- revamp `test/mozilla-ast.js`
  - reuse `test/ufuzz.js` for code generation
  - use `acorn.parse()` for creating `estree`
- extend `test/ufuzz.js` for `acorn` workaround
  - catch variable redefinition
  - non-trivial literal as directive
  - adjust options for tolerance

Miscellaneous
- optional semi-colon when parsing directives

fixes #1914
closes #1915

lib/parse.js

@@ -807,24 +807,20 @@ function parse($TEXT, options) {
         handle_regexp();
         switch (S.token.type) {
           case "string":
-            var dir = false;
-            if (S.in_directives === true) {
-                if ((is_token(peek(), "punc", ";") || peek().nlb) && S.token.raw.indexOf("\\") === -1) {
+            if (S.in_directives) {
+                tmp = peek();
+                if (S.token.raw.indexOf("\\") == -1
+                    && (tmp.nlb
+                        || is_token(tmp, "eof")
+                        || is_token(tmp, "punc", ";")
+                        || is_token(tmp, "punc", "}"))) {
                     S.input.add_directive(S.token.value);
                 } else {
                     S.in_directives = false;
                 }
             }
             var dir = S.in_directives, stat = simple_statement();
-            if (dir) {
-                return new AST_Directive({
-                    start : stat.body.start,
-                    end   : stat.body.end,
-                    quote : stat.body.quote,
-                    value : stat.body.value,
-                });
-            }
-            return stat;
+            return dir ? new AST_Directive(stat.body) : stat;
           case "num":
           case "regexp":
           case "operator":