[cpu] Reimplement CPUID features as util::bitset

The cpu::cpu_id class no longer looks up all known features in the
constructor, but instead provides access to the map of supported
features as a bitset from the verify() method. It also exposes the
brand_name() method instead of loading the brand name string in the
constructor and storing it as part of the object.

src/libraries/util/util.module

@@ -9,6 +9,7 @@ module("util",
     public_headers = [
         "util/basic_types.h",
         "util/bip_buffer.h",
+        "util/bitset.h",
         "util/counted.h",
         "util/deque.h",
         "util/enum_bitfields.h",