Add ARMv8/AArch64 Crypto Extension implementation of SHA-1

* cipher/Makefile.am: Add 'sha1-armv8-aarch64-ce.S'.
* cipher/sha1-armv8-aarch64-ce.S: New.
* cipher/sha1.c (USE_ARM_CE): Enable on ARMv8/AArch64.
* configure.ac: Add 'sha1-armv8-aarch64-ce.lo'.

Benchmark on Cortex-A53 (1152 Mhz):

Before:

|  nanosecs/byte   mebibytes/sec   cycles/byte

SHA1 | 7.54 ns/B 126.4 MiB/s 8.69 c/B

After (4.3x faster):

|  nanosecs/byte   mebibytes/sec   cycles/byte

SHA1 | 1.72 ns/B 553.0 MiB/s 1.99 c/B

• Signed-off-by: Jussi Kivilinna <jussi.kivilinna@iki.fi>