I haven't used g++ for quite a while now, but IIRC something you needed to do was, if you're using gcc to do the linking for you (eg gcc -omybin myobj1.o myobj2.o myobj3.o) is that you have to use the g++ command to do this, as gcc is the C compiler and g++, being the C++ compiler, does a bit more. If you're using ld to link the final binary, you'd have to add "-lstdc++" or "-lstdcxx" to your command line (that's part of that extra stuff g++ does). That library has all the stream code in it.
So, according to your example, you should be doing this:
Projects:test> g++ -o vex vex.cpp
(if g++ is not recognized as a command, try gxx)