Enable UPnP port mapping support

Packages describing “upnp” as local USE flag

Package“upnp” Flag Description
media-video/vlcEnable support for the Intel SDK stack based UPnP discovery module instead of CyberLink
net-im/gajimAbility to request your router to forward port for file transfer
net-p2p/bitcoin-coreEnable Universal Plug and Play
net-p2p/bitcoindEnable Universal Plug and Play
net-p2p/bitcoin-qtEnable Universal Plug and Play
net-p2p/ktorrentForward ports using UPnP

All packages providing a “upnp” USE flag (22)