Decompresses a chm block. Depending on chm block type chooses most relevant
decompressing method. A chm block type can be as follows:
- no action taken, i.e. skipping the block
UNCOMPRESSED the most simplest In addition there are unknown types (4-7).
Currently relying on previous chm block these types changing according to the
previous chm block type. We need to invent more appropriate way to handle