Just correspond with nixpkgs master and staging. More to likely come.

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.

Had a few issues with non existing source files and output.