Wow... this is actually a much bigger issue, because we deliberately haven't yet used any C++11 features directly in Inkscape.
We could, as you suggest, only enforce C++11 builds for people with new versions of libsigc++, but it makes me pretty nervous having to support two different C++ standards.
A proper fix would enforce C++11 builds for everyone, but this is problematic, because AFAIK older OS X releases don't provide compiler support for C++11.
Wow... this is actually a much bigger issue, because we deliberately haven't yet used any C++11 features directly in Inkscape.
We could, as you suggest, only enforce C++11 builds for people with new versions of libsigc++, but it makes me pretty nervous having to support two different C++ standards.
A proper fix would enforce C++11 builds for everyone, but this is problematic, because AFAIK older OS X releases don't provide compiler support for C++11.
I think this needs further discussion! :/