make: Create include directory for make install to install headers.  Put ndn-cpp-config.h in include/ndn-cpp.
diff --git a/ndn-cpp/c/common.h b/ndn-cpp/c/common.h
index 72af018..48e2ec2 100644
--- a/ndn-cpp/c/common.h
+++ b/ndn-cpp/c/common.h
@@ -7,7 +7,7 @@
 #ifndef NDN_COMMON_H
 #define	NDN_COMMON_H
 
-#include "../ndn-cpp-config.h"
+#include <ndn-cpp/ndn-cpp-config.h>
 #include <stdint.h>
 #include <stddef.h>