c/util: Making util/crypto.h a public header

Change-Id: Ie63d3b5b206ae7e027e11077b6c0a039ed75eb92
diff --git a/include/Makefile.am b/include/Makefile.am
index 2f0a01d..d2729b4 100644
--- a/include/Makefile.am
+++ b/include/Makefile.am
@@ -8,7 +8,8 @@
 ndn_cpp_c_headers = \
   $(wildcard ndn-cpp/*.h) \
   $(wildcard ndn-cpp/c/*.*) \
-  $(wildcard ndn-cpp/c/encoding/*.*)
+  $(wildcard ndn-cpp/c/encoding/*.*) \
+  $(wildcard ndn-cpp/c/util/*.*)
 
 # Public C++ headers.
 # Use ndn-cpp/*.hpp instead of *.* to not overwrite *.h from above.