Thanks for working on this. However, Eli asked for --with-pop to remain 
the default on native MS-Windows. Also, I found the newly-added warnings 
confusing (though admittedly everything is confusing here :-).

How about the attached patch instead? It does not change the 
configure-time warnings. It merely changes the default, so that 
--without-pop is now the default on platforms other than native MS-Windows.