make: Create include directory for make install to install headers. Put ndn-cpp-config.h in include/ndn-cpp.
diff --git a/Makefile.am b/Makefile.am
index dc13961..b926a93 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -9,6 +9,9 @@
## to provide a way for the user to supply additional arguments.
ACLOCAL_AMFLAGS = ${ACLOCAL_FLAGS} -I m4
+# "make install" will also install the include headers.
+SUBDIRS = include
+
lib_LTLIBRARIES = libndn-c.la libndn-cpp.la
bin_PROGRAMS = bin/test-encode-decode-forwarding-entry bin/test-encode-decode-interest bin/test-encode-decode-data \