We were cating UBsan findings under Clang similar to "adv-simd.h:1138:26: runtime error: addition of unsigned offset to 0x000002d41410 overflowed to 0x000002d41400". The problem was CRYPTOPP_CONSTANT, which used an enum. The compiler is allowed to pick the underlying data type, and Clang was picking a signed type
This also fixes the SPECK64 bug where CTR mode self tests fail. It was an odd failure because it only affected 64-bit SPECK. SIMON was fine and it used nearly the same code. We tracked it down through trial and error to the table based rotates.