[boost] Correction:building with VC++ 8.0 Express beta

Sorry for jumpng the gun : downloading MSDN Libarary for Express VC++ 8.0 beta took a whole night. First, there is no single-threaded static CRT anymore. Documentation suggests to use multi-threaded CRT also for single-threaded programs. /MT and /MD (and corresponding MTd and MDd for debug mode) determine if CRT code will be linked with the program or if CRT DLL will be dynamically loaded. Documentation does not suggest any substitute for /Gs option while it suggests /O1 or /O2 instead of /Og. Tony