add .overrideDerivation and .overrideAttrs to packages created with...

add .overrideDerivation and .overrideAttrs to packages created with `callPackages`/`callPackagesWith`

nix/nixUnstable, tomcatN and postgresqlNN use `callPackages` pattern, they have .override
attribute, but lack .overrideDerivation and recent .overrideAttrs.
Packages created with `callPackage` have all of those. Because .overrideDerivation function
is used in public, without this we can break code when refactoring callPackage -> callPackages.