libmodbus: include licensing information

Signed-off-by: Michael Heimpold <mhei@heimpold.de>

libs/libmodbus/Makefile

@@ -15,6 +15,11 @@ PKG_SOURCE:=$(PKG_NAME)-$(PKG_VERSION).tar.gz
 PKG_SOURCE_URL:=http://libmodbus.org/releases
 PKG_MD5SUM:=c80f88b6ca19cabc4ceffc195ca07771
 
+PKG_MAINTAINER:=Michael Heimpold <mhei@heimpold.de>
+
+PKG_LICENSE:=GPL-3.0+ LGPL-2.1+
+PKG_LICENSE_FILES:=COPYING COPYING.LESSER
+
 PKG_FIXUP:=autoreconf
 PKG_INSTALL:=1
 
@@ -25,11 +30,10 @@ define Package/libmodbus
   CATEGORY:=Libraries
   URL:=http://www.libmodbus.org
   TITLE:=libmodbus
-  MAINTAINER:=Michael Heimpold <mhei@heimpold.de>
 endef
 
 define Package/libmodbus/description
-A Modbus library for Linux, Mac OS X, FreeBSD, QNX and Win32
+  A Modbus library for Linux, Mac OS X, FreeBSD, QNX and Win32.
 endef
 
 TARGET_CFLAGS += $(FPIC)