v0.9.1-prerelease - this is incremental fixes over 0.9.0-prelease found during review

This is effectively a service pack for the previous release, fixing issues which have been found.

What's Changed

Noting redundant cases in encodings:

• Reserve redundant SCBNDSI encodings by Alexander Richardson (@arichardson) in #418
• Mark c0-authorized loads and stores as extensible by Nathaniel Wesley Filardo (@nwf) in #403

Spec changes (4 PRs to achieve the ACPERM solution)

• clarify ACPERM rules by Tariq Kurd (@tariqkurd-repo) in #421
• apply ACPERM rules in order by Tariq Kurd (@tariqkurd-repo) in #427
• Fix typo in ACPERM rules by Tom Aird (@tomaird) in #429
• Fix RV32 Zcherilevels ACPERM by Tariq Kurd (@tariqkurd-repo) in #440

extension implication rules

• vm requires pte scheme by Tariq Kurd (@tariqkurd-repo) in #447

typos and minor fixes

• typos and minor fixes by Tariq Kurd (@tariqkurd-repo) in #409
• Makefile: fix the version number by Martin Kaiser (@martin-kaiser) in #412
• fix LC encoding diagram by Tariq Kurd (@tariqkurd-repo) in #414
• Xtval2 clarification by Tariq Kurd (@tariqkurd-repo) in #419
• clarify writes to dinfc by Tariq Kurd (@tariqkurd-repo) in #417
• improve dinfc wording by Tariq Kurd (@tariqkurd-repo) in #420
• level-ext: fix permission encoding table by Martin Kaiser (@martin-kaiser) in #423
• sort out extensions xrefs by Tariq Kurd (@tariqkurd-repo) in #422
• Adding comma to list by ricki-code in #425
• Add CL to null cap table by Tom Aird (@tomaird) in #430
• Fix minor typo in PTE section by Tim Hutt (@Timmmm) in #433
• add missing words by Tariq Kurd (@tariqkurd-repo) in #435
• Add SL description to all store cap instructions by Tom Aird (@tomaird) in #431
• add CL rules for CBLD and SCSS by Tariq Kurd (@tariqkurd-repo) in #437
• local/global clarification by Tariq Kurd (@tariqkurd-repo) in #436
• Clarify interaction of levels with sealed capabilities by Alexander Richardson (@arichardson) in #439
• clarify that quad 2 and 3 entries 4 and 5 are reserved when LVLBITS=2 by Tariq Kurd (@tariqkurd-repo) in #442
• Xstatus.CRG clarification by Tariq Kurd (@tariqkurd-repo) in #443
• reinstate mstatus.CRG with justification by Tariq Kurd (@tariqkurd-repo) in #445
• replace incorrect constants with variables for pcc.M by Tariq Kurd (@tariqkurd-repo) in #444
• Clarify behaviour of vstid/vstidc registers. by Paul Buxton (@buxtonpaul) in #446

New Contributors

• Nathaniel Wesley Filardo (@nwf) made their first contribution in #403

Full Changelog: v0.9.0-prerelease...v0.9.1-prelease