cbits: Add ARM NEON SIMD support
cbits: Add ARM NEON SIMD support

This commit adds the appropriate NEON SIMD instructions in the
`reedsolomon_gal_mul_*` framework.

No tests at the Haskell level were performed to validate the correctness
of these changes. The tests introduced in 245025d39 were used, with
success.

See: 6282161457cc778dded715c3e6b7e167f6557cbc
See: 245025d399d404e589dbf183e6576caeb5822be9

NicolasT/reedsolomon,NicolasT/reedsolomon