libconfig: add license information

Signed-off-by: Simon Dawson <spdawson@gmail.com>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>

package/libconfig/libconfig.mk

@@ -3,8 +3,11 @@
 # libconfig
 #
 #############################################################
+
 LIBCONFIG_VERSION = 1.4.8
 LIBCONFIG_SITE = http://www.hyperrealm.com/libconfig/
+LIBCONFIG_LICENSE = LGPLv2.1+
+LIBCONFIG_LICENSE_FILES = COPYING.LIB
 LIBCONFIG_INSTALL_STAGING = YES
 LIBCONFIG_CONF_OPT = --disable-examples