Support hardware SHA-256 and SHA-1 on Arm platforms.

Similarly to my recent addition of NEON-accelerated AES, these new
implementations drop in alongside the SHA-NI ones, under a different
set of ifdefs. All the details of selection and detection are
essentially the same as they were for the AES code.

windows/winmiscs.c

@@ -283,4 +283,14 @@ bool platform_aes_hw_available(void)
     return IsProcessorFeaturePresent(PF_ARM_V8_CRYPTO_INSTRUCTIONS_AVAILABLE);
 }
 
+bool platform_sha256_hw_available(void)
+{
+    return IsProcessorFeaturePresent(PF_ARM_V8_CRYPTO_INSTRUCTIONS_AVAILABLE);
+}
+
+bool platform_sha1_hw_available(void)
+{
+    return IsProcessorFeaturePresent(PF_ARM_V8_CRYPTO_INSTRUCTIONS_AVAILABLE);
+}
+
 #endif