Fixes bug 20587 - Add K&R break before braces style

Summary:
http://llvm.org/bugs/show_bug.cgi?id=20587

Added K&R style. It could be enabled by the following option:

```
BreakBeforeBraces: KernighanRitchie
```

This style is like `Attach`, but break *only* before function
declarations.

As I can see, no additional logic required to support this style, any
style different from other styles automagically satisfies K&R.

Reviewers: djasper

Reviewed By: djasper

Subscribers: cfe-commits, klimek

Differential Revision: http://reviews.llvm.org/D4837

llvm-svn: 215354