Lets you list out what files were removed from OLD to NEW generations. Note
automatically done to remove files as I consider that the job of the user.

While here, added a function check_defined to let me check if a variable is
defined or not and if not bail.

Updated the option target to use this function as well as the removed target
where I needed it for.

Works around stuff like vpn dns setting its own hostname
and hostname -s to return that dns name verus the configured
name for the mac.

uname -n uses/catches dhcp addresses, which is dumb.

Switch to use tangle/file everywhere. Lots of cleanup.

Also define option predicates via the makefile option of:

make option NAME=whatever

Which defines the options in options/whatever.el and
options/no-whatever.el

Switch from using osx-p to macos-p now for osx.

There were a few other changes that snuck in that I was too
lazy to split apart. But all this should make this all simpler.

It also means you can edit source blocks in emacs sanely.