Add `package--builtins' to `nix-emacs-included-packages'.

Signed-off-by: Moritz Ulrich <moritz@tarn-vedra.de>
Be smarter about which packages to include/exclude.

Signed-off-by: Moritz Ulrich <moritz@tarn-vedra.de>
Merge branch 'emacs-package-el' into emacs-packages-updates

Signed-off-by: Moritz Ulrich <moritz@tarn-vedra.de>
Update emacs-packages-generated.nix.

Signed-off-by: Moritz Ulrich <moritz@tarn-vedra.de>