Added C crypto.c for digestSha256
diff --git a/Makefile.am b/Makefile.am
index 53eb83f..10297a0 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -34,6 +34,7 @@
   ndn-cpp/c/transport/socket-transport.c ndn-cpp/c/transport/socket-transport.h \
   ndn-cpp/c/transport/tcp-transport.h \
   ndn-cpp/c/transport/udp-transport.h \
+  ndn-cpp/c/util/crypto.c ndn-cpp/c/util/crypto.h \
   ndn-cpp/c/util/dynamic-uchar-array.c ndn-cpp/c/util/dynamic-uchar-array.h \
   ndn-cpp/c/util/ndn_memory.c ndn-cpp/c/util/ndn_memory.h \
   ndn-cpp/c/util/ndn_realloc.c ndn-cpp/c/util/ndn_realloc.h