Initial import of libdpf.

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

thirdparty/portable-snippets/exact-int/README.md

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+# Exact-Width Integer Types
+
+Lots of stuff in psnip (as well as outside of psnip) requires
+exact-width integer types.  C99 provides them in `<stdint.h>`, but
+sometimes you can't rely on C99 being available.
+
+This header will define macros for `psnip_(u)int(8,16,32,64)_t`, using
+methods a bit more portable than just blindly including `<stdint.h>`:
+
+ * If `__(U)INTN_TYPE__` is defined, use those types.
+ * On platforms where we know `<stdint.h>` is available (such as if
+   we're compiling in C99 mode), we include `<stdint.h>`.
+ * Otherwise, if we're using Visual Studio, use types we know exist.
+ * If not, use `<limits.h>` to try to find some correctly-size types.
+
+Headers in portable-snippets which use these types will only try to
+include `exact-int.h` if they are missing a type they actually use,
+which means you're free to create your own definitions for these
+types.  This should help ensure that, if you already have exact-size
+types, portable-snippets will be compatible with them.
+
+If are looking for a more complete portable implementation of
+`<stdint.h>` (for example, if you need the `UINT*_C` macros), there
+are several projects which aim to provide a more complete
+implementation, including:
+
+ * [pstdint.h](http://www.azillionmonkeys.com/qed/pstdint.h) (BSD-3)
+ * [msinttypes](https://code.google.com/archive/p/msinttypes/) (BSD-3)
+
+Feel free to file a PR if I'm missing anything.