rename staging to unstable

See merge request iris/iris!826

logatom_lock tweaks

See merge request iris/iris!829

track has_lc directly in invGS/irisGS/heapGS rather than via separate typeclass

See merge request iris/iris!816

[Docs] Add "Fira Code Retina" instructions for Linux

See merge request iris/iris!824

see https://github.com/tonsky/FiraCode/wiki/VS-Code-Instructions

Fix a proof broken on Coq master

See merge request iris/iris!822

Add later credits to the WP

See merge request iris/iris!808

Make validy lemmas for `excl_auth` and `(u)frac_auth` more consistent with `auth`.

See merge request iris/iris!804

and `frac_auth_frag_valid_op_1_l`, add `frac_auth_frag_op_validN` and
`frac_auth_frag_op_valid`, which are bi-implications with arbitrary fractions.

Remove unused Qp argument to dfrac_valid_discarded

See merge request iris/iris!819

add mono_nat_lb_own_0

See merge request iris/iris!817

general lemma that a fixpoint is Persistent/Absorbing/Affine

See merge request iris/iris!810

Make saved props have discardable fractions

See merge request iris/iris!802

Tweak priority of proof mode instances for £.

Closes #470

See merge request iris/iris!818