doc: Update PortingNotes.
r6rs-common: Add (yuni compat keywords)
r7rs: Move several chibi-yuni => r7rs-common-yuni
guile: Initial commit for guile support (not working yet)
build-nmosh: Use R6RS library syntax for stub libraries
guile: First light
doc: Update PortingNotes
picrin: Prepare
doc: Update PortingNotes