doc: adds todo
config: adds Emacs major-mode mark in setup-file

so Emacs knows our .setup file is really a .scm file
build: use std=gnu99 instead of c99

because the new version of chicken.h won't work with c99, but it works
with gnu99 so we'll try to use that as long as that works.

note that it's tricky to remove std entirely because the warnings are
coming from the for loops in chicken_private.h which are currently
installed independently from this egg.