Add support for AArch32 CRC32 and CRC32C instructions added in ARMv8
and add a CPU feature flag to enable these instructions.

The CRC32-C implementation used is the built-in qemu implementation
and The CRC-32 implementation is from zlib. This requires adding zlib
to LIBS to ensure it is linked for the linux-user binary.
Signed-off-by: NWill Newton <will.newton@linaro.org>
Reviewed-by: NPeter Maydell <peter.maydell@linaro.org>
Message-id: 1393411566-24104-3-git-send-email-will.newton@linaro.org
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>