need -lrt, always
Fixes for optional_test:

      Added missing #include

      Upgraded to the latest intel-win32-tools.jam in order to handle
      intel5 compatibility.
Fix locale support for metrowerks
Fix facet support for intel-win32
Correctly signal that wchar_t is not a distinct type when emulating vc6.
Fixed runtime library choice, since STLPort offers only multithreaded builds
Preserve PATH from environment
Fix relative path bug