This fixes handle_contract_violation under versioned namespace mode. Tested under Linux x64 and confirmed to also fix Darwin build. libstdc++: [_GLIBCXX_INLINE_VERSION] Provide handle_contract_violation symbol libstdc++-v3/ChangeLog:         * src/experimental/contract.cc         [_GLIBCXX_INLINE_VERSION](handle_contract_violation): Provide symbol         without version namespace decoration for gcc. François