[boost] [system] Minor changes to compile on linux

Couple last issues. Compiling error_code.cpp although it's apparently not actually needed for the cpu_timer test: ../../../boost/system/error_code.hpp:152: error: no ‘boost::system::errno_t boost::system::error_code::erno_value() const’ member function declared in class ‘boost::system::error_code’ inline errno_t error_code::erno_value() const ^^^^^^^ inline errno_t error_code::errno_value() const error_code.cpp: In function ‘void boost::system::system_message(boost::system::error_code, std::string&)’: error_code.cpp:234: error: ‘sys_err_code’ was not declared in this scope Change error_code.cpp::235 to target += std::strerror( ec.sysno_value() ); Jeff