Updated Debian example bitcoin.conf

Here I am using the base config from wiki and I have removed some cruft as per developers' advices; comments updated accordingly.

See also https://github.com/bitcoin/bitcoin/pull/4306
`*` doesn't work anyomoer as a wildcard character. It's not deprecated, it will give an error.
A bare rpcallowip=ip like `rpcallowip=10.1.1.34` will also still work.