[boost] [system] patch for error_code.cpp

From: Boris Gubenko (Boris.Gubenko_at_[hidden])
Date: 2007-06-08 15:13:00

Module libs/system/src/error_code.cpp has conditionalization which ensures
that strerror_r() is called only on the platforms where this function is
availble.

The condition does not take into account Tru64 and VMS and, as a result,
the module does not compile on these platforms. Attached patch fixes this
problem.

Ok to commit to HEAD?

Thanks,
  Boris