autoconf: readline dependency is mendatory

configure.ac

@@ -79,7 +79,9 @@ PKG_CHECK_MODULES([msgpack], [msgpack >= 1.1])
 AC_ARG_ENABLE([tools], AS_HELP_STRING([--disable-tools],[Disable tools (CLI DHT node)]),,build_tools=yes)
 AM_CONDITIONAL(ENABLE_TOOLS, test x$build_tools == xyes)
 AM_COND_IF([ENABLE_TOOLS], [
-    AC_CHECK_HEADERS([readline/readline.h readline/history.h])
+  AC_CHECK_HEADERS([readline/readline.h readline/history.h], [], [
+    AC_MSG_ERROR([unable to find readline.h])
+  ])
 ])
 
 AM_COND_IF([HAVE_DOXYGEN], [AC_CONFIG_FILES([doc/Doxyfile doc/Makefile])])

tools/Makefile.am

@@ -3,10 +3,10 @@ bin_PROGRAMS = dhtnode dhtchat dhtscanner
 AM_CPPFLAGS = -I../include
 
 dhtnode_SOURCES = dhtnode.cpp
-dhtnode_LDFLAGS = -lopendht -L../src/.libs @GNUTLS_LIBS@
+dhtnode_LDFLAGS = -lopendht -lreadline -L../src/.libs @GNUTLS_LIBS@
 
 dhtchat_SOURCES = dhtchat.cpp
-dhtchat_LDFLAGS = -lopendht -L../src/.libs  @GNUTLS_LIBS@
+dhtchat_LDFLAGS = -lopendht -lreadline -L../src/.libs  @GNUTLS_LIBS@
 
 dhtscanner_SOURCES = dhtscanner.cpp
-dhtscanner_LDFLAGS = -lopendht -L../src/.libs  @GNUTLS_LIBS@
+dhtscanner_LDFLAGS = -lopendht -lreadline -L../src/.libs  @GNUTLS_LIBS@