deflate_compress: adjust block splitting conditions
deflate_compress: adjust block splitting conditions

For fastest, greedy, lazy, and lazy2: save memory by reducing the length
of the sequence store, and forcing a split if it is filled.

For fastest: increase the max block length, but use a relatively short
sequence store that will cause shorter blocks to be used often.

For all: allow the final block to exceed the soft maximum length if it
avoids having to create a block below the minimum length.

ebiggers/libdeflate,ebiggers/libdeflate,ebiggers/libdeflate