add license
Merge branch 'master' into dev
Merge remote-tracking branch 'origin/master' into dev
Format adjustment.

1. Remove all '\r'.
2. Use spaces for indent.
3. Convert all "#pragma once" to "#ifndef .../#define .../#endif".
Make the library and demo code buildable for Android.

It can be only built but does not run well yet. During running,
Segmentation Fault happens. I will debug it later.