Make .ctors section writable
This is needed for PIE.
Add mechanism to control use of assembly implementations
Rewrite CPU feature detection
Use assembly to make it run as a constructor.
Move definitions from blake3_impl.h to their corresponding source files
Remove BLAKE3_TESTING guards
To disable asserts, just build with -D NDEBUG.
Add Makefile and b3sum utility
Remove unnecessary immintrin.h include
Inline counter_low and counter_high
Move CPU feature detection to assembly source