[Agda] 2.6.4-rc1

[mechvel at scico.botik.ru]

I have tested Agda 2.6.3.20230805

built with flags (cabal -f)
   - optimise-heavily: extra optimizations

with ghc 9.2.7 under Ubuntu Linux 18.04.

My large computer algebra library is type-checked as

     agda $agdaLibOpt --auto-inline --guardedness TypeCheckAll.agda

Then it is compiled, and Test is run.

This works like in Agda 2.6.3,
except that I was forced to change Level.zero to a more appropriate one 
in several places.

--
SM