5.4.0

As usual there are many bug fixes, improvements to system call coverage, and incremental performance improvements. Thanks to all our contributors.

AMD Zen CPUs are now supported, with some caveats. Special thanks to the people who reverse-engineered Zen details to enable this.

There is experimental support for ARM AArch64 platforms that avoid the STREX instruction.

rr record has a new option --nested=detach which lets nested rr recordings run "detached" to create a separate recording.