Follow-up: B5cxx11 is abi:cxx11, which is described here:
https://gcc.gnu.org/onlinedocs/libstdc++/manual/using_dual_abi.html
According to that, abi:cxx11 can be removed from symbols by adding this (e.g. to CMakeLists.txt):
add_definitions(-D_GLIBCXX_USE_CXX11_ABI=0)
The symbol for the GetObjectDescription() method is afflicted because it returns a string, and the ABI for strings changed between c++98 and c++11.