First, BuildHuffmanTable is called to check if the data is valid.
If it is and the table is not big enough, more memory is allocated.
This will make sure that valid (but unoptimized because of unbalanced
codes) streams are still decodable.
Bug: chromium:1479274
Change-Id: I31c36dbf3aa78d35ecf38706b50464fd3d375741
this avoids duplicates between these trees and dsp/, e.g., enc/tree.c,
dec/tree.c, making pulling the whole library source tree into one target
possible
BUG=webp:279
Change-Id: I060a614833c7c24ddd37bf641702ae6a5eef1775