page_zip_malloc(): Replace ut_malloc(...) with mem_heap_alloc(opaque, ...).

page_zip_free(): Dummy function (cannot deallocate from InnoDB memory
heaps, and zlib seems to defer deallocation to the very end anyway).

page_zip_compress(): Create a big enough heap for the needs of zlib.
Replace deflateInit() with deflateInit2().

page_zip_decompress(): Create a big enough heap for the needs of zlib.
Replace inflateInit() with inflateInit2().