page_zip_compress(), page_zip_decompress_low(), page_zip_reorganize():
Make use of memcpy_aligned() and memset_aligned(), so that some
operations can be translated more efficiently.

No difference was observed for AMD64 on GCC 9.2.1. But, such hints could
enable more efficient code on less common instruction set architectures,
such as 32-bit ARM, POWER or MIPS.