Replace the temporary file hack currently used to change Bitcoin-Qt's dock icon (OS X) with a buffer-based solution.
Add built-in seeds for .onion

This makes it possible for a node with `-onlynet=tor` to bootstrap
itself.

It also adds the base infrastructure for adding IPv6 seed nodes.

Also represent IPv4 fixed seed addresses in 16-byte format.

Conflicts:
	src/Makefile.am
	src/chainparams.cpp