[CLN-list] CLN switched to C++11

Hi, I've just just bumped the minimum C++ language support for the compiler to C++11. I did this because C++11 is a better language and it's widely supported by now. Sticking to C++98 would require us to sometimes write convoluted patches. All in all it's a minor thing: configure makes sure that proper compiler options are chosen and the change doesn't even break the ABI. Still, I thought I should announce this here. All my best,    -richy.