impl: rename 'detail' to 'impl'

'impl' directory contains implementation-detail headers that are NOT
installed. 'detail' directory will be used for implementation-detail
headers that ARE installed.

refs #4782

Change-Id: I13428e032c93207753a6b856c693511c4fc3bbb8
diff --git a/tools/ndnsec/util.cpp b/tools/ndnsec/util.cpp
index f5069e7..5e5c341 100644
--- a/tools/ndnsec/util.cpp
+++ b/tools/ndnsec/util.cpp
@@ -21,7 +21,7 @@
 
 #include "util.hpp"
 
-#include "ndn-cxx/security/detail/openssl.hpp"
+#include "ndn-cxx/security/impl/openssl.hpp"
 
 namespace ndn {
 namespace ndnsec {