[PATCH 00/12] aarch64: Extend aarch64_feature_flags to 128 bits

[Andrew Carlotti <andrew.carlotti@arm.com>]

The end goal of the series is to change the definition of aarch64_feature_flags
from a uint64_t typedef to a class with 128 bits of storage.  This class uses
operator overloading to mimic the existing integer interface as much as
possible, but with added restrictions to facilate type checking and
extensibility.

Patches 01-10 are preliminary enablement work, and have passed regression
testing.  Are these ok for master?

Patch 11 is an RFC, and the only patch that touches the middle end.  I am
seeking clarity on which part(s) of the compiler should be expected to handle
or prevent non-bool types in instruction pattern conditions.  The actual patch
does not compile by itself (though it does in combination with 12/12), but that
is not important to the questions I'm asking.

Patch 12 is then a small patch that actually replaces the uint64_t typedef with
a class.  I think this patch is fine in it's current form, but it depends on a
resolution to the issues in patch 11/12 first.