Further update liquid-fixpoint.cabal to release 0.9.6.3.1

Bump version to 0.9.6.3 and update the changelog

Add CHANGES.md and README.md to extra-doc-files

Bump version to 0.9.2.5

update version for release

Merge pull request #501 from facundominguez/fd/ghc-8.10.7

Update stack snapshot to build with ghc-8.10.7

Fixing uniq

bump cabal version

bump LF version to 0.7