Most relevant commits:
- native: use 'Declaration' type for a declaration
- compiler/checker: make clearer an error message loading a package
- native: revert 'make 'MapPackage' methods with pointer receivers'
- native: rename 'Package.Name' method to 'PackageName'
- native: fix 'CombinedPackage.PackageName' method documentation
- compiler/checker: fix import of native packages with not allowed names
- native: replace 'Package.DeclarationNames' method with 'LookupFunc'