[PATCH] Added instruction combine to transform few more negative values addition to subtraction (Part 2)

[Jingyue Wu]

Hi Dinesh, 

I didn't see the code handling the second case in your summary: 
```
(x + (~((y >> z) | c) + 1)   -->   x - ((y>>z) | c)  if c is even
```

Am I missing anything? 

Thanks,
Jingyue

http://reviews.llvm.org/D4209