Initial import of libdpf.

Co-authored-by: Cursor <cursoragent@cursor.com>

thirdparty/portable-snippets/cpu/README.md

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+# CPU Information
+
+This module provides an API for querying some CPU features, such as
+ISA extension support, that works across multiple architectures and
+platforms.
+
+## Dependencies
+
+This module requires the once portable-snippet module.  If you do not
+include once.h before cpu.h, cpu.h will automatically include
+"../once/once.h".  If you include once.h manually you are free to use
+whatever directory structure you like.
+
+## Limitations
+
+This code currently only supports x86/x86-64 and ARM.