Make the number of columns static in PHS mode.
Be a little more verbose while testing.
LYRA2-REF: Import the reference package for Lyra2.
LYRA2-REF: Don't #include omp.h in single-threaded mode.
LYRA2-REF: Remove some compiler flags that are not available on clang.
LYRA2-REF: Reuse random column in the final absorb.
Ignore compilation results for the reference implementation.
Also clean reference implementation on `make clean`.
LYRA2-REF: Accept extra CFLAGS and a main.c when building the sse2 version.
Add `ref` and a `bench-ref` targets.
Add a simple benchmark script.