Fix HTTPFetch caller and request ID to 64 bits
Check that allocated caller ID is not DISCARD
Print body if serverlist request returns error
Don't print control characters from HTTP responses
Document special HTTPFetch caller IDs
Allow unicode to be printed
The fallback code shouldn't be needed and is a remnant of the GET
method that old media servers use. Clients using it are likely
to just waste bandwidth and having to download the media again
through the normal transfer from server method. The most reliable
method is to get all missing textures therefore from the server
directly and not spam the remote media server with 404s.
