[VIRT-294 # ARMv8.3-PAuth, Pointer Authentication ]

Fixed HCR/SCR enablement of API/APK. Posted v2 of the prctl.

[VIRT-339 # ARMv8.5-BTI, Branch Target Identification ]

Posted v2.

[VIRT-327 # Richard's upstream QEMU work ]

Implemented variable-length decoding in scripts/decodetree.py. Lots of fiddling about with the RX ISA to understand what was actually needed within decodetree.

Pull request for vector extensions and dynamic tlb sizing.

Finished MPS review.

r~