Changes from original BLAKE3 sources:
* `blake.h`:
* Changes to avoid conflicts if a client also links with its own BLAKE3 version:
* Renamed the header macro guard with `LLVM_C_` prefix
* Renamed the C symbols to add the `llvm_` prefix
* Added a top header comment that references the CC0 license and points to the `LICENSE` file in the repo.
* `blake3_impl.h`: Added `#define`s to remove some of `llvm_` prefixes for the rest of the internal implementation.
* Implementation files:
* Added a top header comment for `blake.c`
* Used `llvm_` prefix for the C public API functions
* Used `LLVM_LIBRARY_VISIBILITY` for internal implementation functions
* Added `.private_extern`/`.hidden` in assembly files to reduce visibility of the internal implementation functions
* `README.md`:
* added a note about where the sources originated from
* Used the C++ BLAKE3 class and `llvm_` prefixed C API in place of examples and API documentation.
* Removed instructions about how to build the files.
7f05aa2d4c