elang/compiler/testing: Avoid |DCHECK| of |ast::Class::base_classes()| in |CompilerTest::GetBaseClasses()|.
elang/compiler: Use |ast::MemberAccess| to repesent alias and import reference.
elang/compiler: Use |ast::MemberAccess|, |ast::NameReference| and |ast::ConstructedType| as base class specification for |ast::Class|.
elang/compiler: Revise |NamespaceAnalyzer|.
Merge branch 'MemberAccess'