parser不用正确解析以LF为换行格式下多个斜杠开头的comments

### vux-loader version
**^1.0.56**

### OS/Browsers version
无关

### Vue version
**^2.6.0**

### Code
```javascript
/////
const a = 1;

// another comment here
let b = 'this works';
```
### What is Expected?
以`\n`为换行格式的文件能够正确解析多个`/`开头的comments

### What is actually happening?
静态解析初始文本
```
/////\n const a=1;\n\n // another comment here\n let b='this works';\n
```
经过vux-loader解析后 `const a = 1;` 被注释掉了。