package/gdbm: add optional support for readline

readline support was added in version 1.13:

http://puszcza.gnu.org.ua/forum/forum.php?forum_id=1145
"The gdbmtool utility now offers the usual line-editing facilities
 (if the package has been compiled with GNU Readline."

Signed-off-by: Bernd Kuhls <bernd.kuhls@t-online.de>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

package/gdbm/gdbm.mk

@@ -14,4 +14,11 @@ ifeq ($(BR2_PACKAGE_GETTEXT),y)
 GDBM_DEPENDENCIES += gettext
 endif
 
+ifeq ($(BR2_PACKAGE_READLINE),y)
+GDBM_CONF_OPTS += --with-readline
+GDBM_DEPENDENCIES += readline
+else
+GDBM_CONF_OPTS += --without-readline
+endif
+
 $(eval $(autotools-package))