config/literate: expand #+INCLUDE directives
config/literate: expand #+INCLUDE directives

It's surprising that tangling doesn't expand #+INCLUDE directives. It's
so useful for literate configs I decided to expand them manually before
tangling (and relative to DOOMDIR, unless given an absolute path).

hlissner/doom-emacs,hlissner/doom-emacs,hlissner/doom-emacs,hlissner/.emacs.d,hlissner/.emacs.d,hlissner/doom-emacs,hlissner/doom-emacs,hlissner/doom-emacs,hlissner/.emacs.d,hlissner/.emacs.d,hlissner/doom-emacs,hlissner/.emacs.d,hlissner/.emacs.d,hlissner/.emacs.d,hlissner/.emacs.d