decompresses properly.

page_mem_free(): Adjust the temporary condition for zeroing data.

page_zip_compress(): Do not accept Z_STREAM_END from non-final deflate().
Tighten the assertion on c_stream.avail_in.

page_zip_dir_sort(): Note that the high bound is not inclusive.

page_zip_dir_decode(): Remove off-by-one error in page_zip_dir_sort() call.

page_zip_set_extra_bytes(): Add the termination condition that was forgotten
from the second for loop.  Simplify the code a little.

page_zip_decompress(): Do not accept Z_STREAM_END from non-final inflate().
Tighten the assertion on d_stream.avail_out.  Increment heap_status correctly.