re: port-arm/59149: expose id_aa64*_el1 registers to userland

[matthew green <mrg%eterna23.net@localhost>]

i think i'd rather the hwcap method, instead of forcing a
trap-and-emulate for all process startup.

be aware that different cpus on an Arm system may not all
support the same set of cpu features.  there are apps that
end up having to be told to run on one or the other only,
so any choices in libc startup etc should consider this.

(this is also true on intel cpus with both p- and e- cores.)


.mrg.