fix bug: upnp.cpp:78: undefined reference to upnpDiscover

My OS is Ubuntu 12.04.3.
fix this make error:
[ 69%] Built target Keyhotee_automoc
Linking CXX executable bin/Keyhotee
BitShares/libbshare.a(upnp.cpp.o): In function `operator()':
/home/jeffrey/Git/keyhotee/BitShares/src/network/upnp.cpp:78: undefined reference to `upnpDiscover'
/home/jeffrey/Git/keyhotee/BitShares/src/network/upnp.cpp:86: undefined reference to `UPNP_GetValidIGD'
/home/jeffrey/Git/keyhotee/BitShares/src/network/upnp.cpp:145: undefined reference to `freeUPNPDevlist'
/home/jeffrey/Git/keyhotee/BitShares/src/network/upnp.cpp:148: undefined reference to `FreeUPNPUrls'
/home/jeffrey/Git/keyhotee/BitShares/src/network/upnp.cpp:96: undefined reference to `UPNP_GetExternalIPAddress'
/home/jeffrey/Git/keyhotee/BitShares/src/network/upnp.cpp:125: undefined reference to `strupnperror'
/home/jeffrey/Git/keyhotee/BitShares/src/network/upnp.cpp:120: undefined reference to `UPNP_AddPortMapping'
/home/jeffrey/Git/keyhotee/BitShares/src/network/upnp.cpp:136: undefined reference to `UPNP_DeletePortMapping'
/home/jeffrey/Git/keyhotee/BitShares/src/network/upnp.cpp:138: undefined reference to `freeUPNPDevlist'
/home/jeffrey/Git/keyhotee/BitShares/src/network/upnp.cpp:139: undefined reference to `FreeUPNPUrls'