[Io] (refactoring) Add override modifier to functions.
[Io] Add InputMemoryStream class.
[Document] (minor) IniDocument::LoadFromText()

accepts r-value reference, which is required in GCC.
[Test][Android] Implements AssetReader.

- Build on AAssetManager and InputMemoryStream.
[Test][Android] Add IniDocumentSuite and its assets.