`constexpr` requires C++11 - intentional?

just to say that 5f2d87c8 means you now require C++11:

g++  -fPIC -o roundchamber.o -c roundchamber.cc -I/afs/cern.ch/work/a/acboxtest/be-abp-tests/tests/HSC/006_iw2d_ZCqvLC/IW2D/External_libs/gmp-6.0.0 -I/afs/cern.ch/work/a/acboxtest/be-abp-tests/tests/HSC/006_iw2d_ZCqvLC/IW2D/External_libs/mpfr-3.1.2/src -I/afs/cern.ch/work/a/acboxtest/be-abp-tests/tests/HSC/006_iw2d_ZCqvLC/IW2D/External_libs/ALGLIB/mpfr/out -I.
In file included from roundchamber.cc:73:0:
./IW2D.h:16:1: error: ‘constexpr’ does not name a type
 constexpr unsigned int precision = Precision; // Precision as a variable, needed when binding to python
 ^
./IW2D.h:16:1: note: C++11 ‘constexpr’ only available with -std=c++11 or -std=gnu++11

(this might be intentional (but seems not to be mentioned explicitly), or be the default for all users anyway - we just still run some functional tests based on compiling this code on CC7 using the system compilers..)