Add lz4hc image compression format

Smaller than lz4 and decompresses at the same speed. Compression is
a bit slower.

Example saves on old FB APK:
Uncompressed: 44748800 bytes
LZ4: 12443648 bytes
LZ4HC: 11055104 bytes

Generating the image slows down by ~1s per 20MB of image due to
slower compression. Decompression is about the same speed but there
should be a slight speedup since less data needs to be read from
flash.

Added test.

Bug: 22858531

(cherry picked from commit a6e81ed4)

Change-Id: Idd0bbe1ea45fc6ab75a42bfeb0ef250e8b3e2f1b