ucfirst doesn't work properly

```
What steps will reproduce the problem?
1. echo UTF8::ucfirst('пиво');

What is the expected output? What do you see instead?
Output: пиво
Expected: Пиво

What version of the product are you using? On what operating system?
Version 2.3.1


```

Original issue reported on code.google.com by `antikon...@gmail.com` on 9 Oct 2012 at 7:21
