Imported changeset from upstream
Merge branch 'sx-lang-base' into sx-lang-master

Conflicts:
	lang/build/build.go
	lang/build/deps_test.go
	lang/parser/error_test.go
	lang/parser/interface.go
	lang/types/builtins.go
	lang/types/check_test.go
	lang/types/universe.go