gosthash2012_const: Remove unused arrays with constants

This probably would reduce size of the library. And remove
some 'not used' warnings (-Wunused-const-variable).

Previously `Ax' is generated dynamically from `A` and `Pi` in
`GOST3411Init', but in 2013 it is moved into `gosthash2012_precalc.h`.
`Tau' is unrolled and eliminated in 2013 too.