Update libGeoIP/GeoIPUpdate.c

These are issues I ran into testing the https://github.com/maxmind/geoip-api-c/tree/bz/jude-proxy-patch branch (sorry about the delay)

The changes involve changing a few internal "\n"'s to "\r\n"'s that my proxy was tripping over.

The other change is an alternative to https://github.com/maxmind/geoip-api-c/commit/86a0335cca2293a4d2c45ad161b7c606b79990f6, so the Proxy-Authorization line isn't sent at all when the creds aren't present.