comments in the source file indicate you can do a one-line g++ statement. however

1) the include requires (-I) are now broader and as specified wrong;
2) you need to do
cd src/mongo/base
python generate_error_codes.py error_codes.err error_codes.h error_codes.cpp
cd -
cd src/mongo/bson/bsondemo
or something now and that isn't specified;
3) there are then undefined simple msgasserted() or something like that
4) i suspect the vcxproj doesn't work anymore either
5) separately, scons . should probably verify that bsondemo.cpp will build period

i suppose if there are more grandiose plans for c++ client & bson lib cleanups and such in the meantime the build instruction comment could be eliminated, #3 resolved, and #5 done, and vcxproj files deleted? as it wouldn't make sense to release it broken. but fixing would be easy too.