[Qt-creator] C++11 in Creator's source: Update required features

[Daniel Teske]

Hi,

> I thus suggest requiring the subset of C++11 that is implemented by VS 2013,
> g++ 4.7 and clang 3.1 in master.

I was expecting this to be somewhat controversial. But, apparently it isn't. 
We have a consensus on this then.

Now, we need to discuss our coding guidelines regarding those new features. 
While we don't need a coding guideline for each C++ feature, I think for those 
new features it's worth having a guideline on when to use them and how to use 
them.

If anyone wants to propose a coding style, please come forward.

We'll have internal discussions at the Berlin office about specific features, so 
I would expect some coding guideline proposals to come from that.

daniel