Add use of the ARMv8 crc32 instructions when requested.

Add use of the ARMv8 crc32 instructions when requested.

Define the macro Z_ARM_CRC32 at compile time to use the ARMv8
(aarch64) crc32x and crc32b instructions. This code does not check
for the presence of the crc32 instructions. Those instructions are
optional for ARMv8.0, though mandatory for ARMv8.1 and later. The
use of the crc32 instructions is about ten times as fast as the
software braided calculation of the CRC-32. This can noticeably
speed up the decompression of gzip streams.