Multiple string-related changes

- Renamed oglplus::String to oglplus::GLString.
- Renamed oalplus::String to oalplus::ALString.
- Added oglplus::String.
- Added oalplus::String.
- Renamed oglplus::StrCRef to oglplus::GLCStrRef.
- Renamed oalplus::StrCRef to oalplus::ALCStrRef.
- Added oglplus::StrCRef.
- Added oalplus::StrCRef.