lib: Add CRC32-C

This is needed for BTRFS.

Signed-off-by: Marek Behun <marek.behun@nic.cz>

 create mode 100644 lib/crc32c.c
diff --git a/lib/Kconfig b/lib/Kconfig
index 628ef8d..aef940f 100644
--- a/lib/Kconfig
+++ b/lib/Kconfig
@@ -146,6 +146,9 @@
 config MD5
 	bool
 
+config CRC32C
+	bool
+
 endmenu
 
 menu "Compression Support"