Note: document in process. please update as this (initially) is just a quick jotting down

This should hold the proposed (with a chance of making it in), and accepted/implemented changes for ebuild format version 1.
bit hard to do, but a version 0 doc (current internal implementation/behaviour) would be good also.

[Version 0 (or undefined eapi, <=portage-2.0.52*)]

[Version 1]
EAPI=1 required, at some point likely assumed but not yet.
configure phase exists; src_configure is the function.
RDEPEND="${RDEPEND-${DEPEND}}" autosetting no longer exists.
addition of elib function, which notes the file to source, then sources it post global ebuild sourcing.
(proposed) BDEPEND metadata addition.