Initial import of libdpf.

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

thirdparty/portable-snippets/check/README.md

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+# Assertion Checking
+
+This module provide a variety of assert()-style macros.  Unlike the
+standard `assert()` macro from `<assert.h>`, most of these macros are
+typed so the input values can be propogated to the string output on
+failure.
+
+For documentation, µnit offers very similar macros (this module was
+originally based off of the macros from µnit), most of
+[the documentation for them](https://nemequ.github.io/munit/#assertions)
+applies to this module's macros, just substitute the `munit_` namespace
+with `psnip_`.
+
+Additionally, unless you define `PSNIP_CHECK_FAIL_DEFINED`, a failing
+assertion should be considered undefined behavior when `NDEBUG` and/or
+`PSNIP_NDEBUG` is defined.  This allows the compiler to perform
+optimizations which would not otherwise be possible.
+
+## Dependencies
+
+To maximize portability you should #include the exact-int module
+before including check.h, but if you don't want to add the extra
+file to your project you can omit it and this module will simply rely
+on <stdint.h>.  As an alternative you may define the following macros
+to appropriate values yourself:
+
+ * `psnip_int8_t`
+ * `psnip_uint8_t`
+ * `psnip_int16_t`
+ * `psnip_uint16_t`
+ * `psnip_int32_t`
+ * `psnip_uint32_t`
+ * `psnip_int64_t`
+ * `psnip_uint64_t`
+
+Including [Hedley](https://nemequ.github.io/hedley/) before check.h
+will significantly improve compiler support and may improve
+performance.