construct a CMRAExt for Agreement. This completes the CMRAExt for the final world, which completes the entire construction - it's all admit-free! :-))

However, there's still a bad admit left in iris_core...

introduce "CMRAExt", and extension property on CMRAs. We will need it to show that later commutes with star. For now, just assume it holds.

Conflicts:
	coq-ho/iris_ht_rules.v

On branch hackgreement
	modified:   coq-ho/iris_core.v
no changes added to commit (use "git add" and/or "git commit -a")

define view shifts and weakest-pre, and show they are all the things though ought to be (downclosed, non-expansive, monotone)

On branch hackgreement
	modified:   coq-ho/iris_plog.v
no changes added to commit (use "git add" and/or "git commit -a")