added extern "C" for C++ fixes problems when included in C++ library
added extern "C" for C++ fixes problems when included in C++ library

borisz/geoip-api-c,borisz/geoip-api-c,Distrotech/geoip-api-c,Distrotech/geoip-api-c,borisz/geoip-api-c,Distrotech/geoip-api-c