Merge "Explain why there are two licenses in here." am: 7ea5aa9624 am: 7809db48d8 am: 2999cd7058

Original change: https://android-review.googlesource.com/c/platform/external/zopfli/+/1736675

Change-Id: Ic61d9cc2395f0b3fbfd836d9b5fdf7d2a4a5c514