They were in .gitignore with a note saying they would become submodules once
they had somewhere to live. They do now, so they are, and ignoring them would
from here on only hide which commit of each one this tree is built against.
The paths stay cosmic-comp/ and cosmic-session/, which is where cosmic-epoch
puts them, so this repository can be merged with the upstream meta-repo rather
than laid out beside it.
