<p>I know that in the original C++0x standard there was a feature called <code>export</code>.</p>

<p>But I can't find a description or explanation of this feature. What is it supposed to do? Also: which compiler is supporting it?</p>

See
this
explanation for its use
Quite a few compilers don't support it either because it's too new or in the case of gcc - because they disaprove.
This post describes standard support for many compilers.
Visual Studio support for new C / C++ standards?