How does one include TR1?

Different compilers seem to have different ideas about TR1. G++ only seems to accept includes of the type:

#include <tr1/unordered_map>
#include <tr1/memory>
...

While Microsofts compiler only accept:

#include <unordered_map>
#include <memory>
...

As for as I understand TR1, the Microsoft way is the correct one.

Is there a way to get G++ to accept the second version? How does one in general handle TR1 in a portable way?