[boost] como toolset failures

I think that big part of failures in como toolset are due to --a (strict mode) option. This unfortunatelly prevents windows headers from being included. Or more precisely, the exact reasult of including windows headers with --a option on is that compiler chokes on __declspec, which is exactly what I see in results. I'd rather not update como toolset to remove this option, maybe someone more familiar with bjam will do this. B.