MapPort when not USE_UPNP #450

In net.cpp there is a MapPort method. This method is compiled only when the USE_UPNP is defined BUT in various places it's called without checking for USE_UPNP (in net.cpp in method StartNode around line 1699 and in ui.cpp in method OnButtonApply around line 1784). The VC++ doesn't like it.

Three things can be done:

• delete the USE_UPNP define and always compile the code (but this could have problems for systems without the library)
• protect the two calls with #ifdef
• put an #else in net.cpp and define an empty MapPort that does nothing.

Each call is within an if(fHaveUPnP) which means the compiler will optimize it out (since fHaveUPnP is a constant). That way you dont have messy ifdefs all over the place.

You have to tell it to the VC++. Probably the gcc is more flexible (in the same way that the gcc ignore the missing return value of AddKey)

VC++ isnt officially supported (due to odd GUI crap that can happen which causes parts of the GUI to become transparent). Last I heard the current makefile for vc will compiled properly anyway (someone updated it not too long ago).