Add intel hardware assisted crc32c support

Not tested, since I don't have the hardware.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/crc/crc32c.h b/crc/crc32c.h
index 1498db9..cf17136 100644
--- a/crc/crc32c.h
+++ b/crc/crc32c.h
@@ -19,5 +19,6 @@
 #define CRC32C_H
 
 extern uint32_t crc32c(unsigned char const *, unsigned long);
+extern uint32_t crc32c_intel(unsigned char const *, unsigned long);
 
 #endif