[Qt-creator] Using C++11 in Creator's source

[Daniel Teske]

Hi,

since we have branched 3.1 from master, master no longer needs to support OS X 
10.6. As such I propose, that we open up master for those C++11 features that 
are supported by VS 2010, g++ 4.5 and clang 3.1.

I think it's too early to require a newer version of Visual Studio, though 
requiring those 3 compilers gives us both *auto* and *lambda*.

I suspect that in practice the minimum g++ or clang version will be higher, 
since practically no one uses those versions any more. 

We need to extend the coding rules for auto and lambda. Suggestions are 
welcome for that.

Ps:
Keep merges from 3.1 easy, by not unnecessarily rewriting code. Wait until 3.1 
is mostly done.