improve error messages (#1506)

- better inheritance of `Error` sub-classes
- mark parse error against source in CLI

closes #235
closes #348
closes #524
closes #1356
closes #1405

test/mocha/comment.js

@@ -13,7 +13,7 @@ describe("Comment", function() {
 
         var fail = function(e) {
             return e instanceof uglify.JS_Parse_Error &&
-                e.message === "SyntaxError: Unexpected token: operator (>)" &&
+                e.message === "Unexpected token: operator (>)" &&
                 e.line === 2 &&
                 e.col === 0;
         }
@@ -36,7 +36,7 @@ describe("Comment", function() {
 
         var fail = function(e) {
             return e instanceof uglify.JS_Parse_Error &&
-                e.message === "SyntaxError: Unexpected token: operator (>)" &&
+                e.message === "Unexpected token: operator (>)" &&
                 e.line === 5 &&
                 e.col === 0;
         }