pptp-linux: add license information

Signed-off-by: Gilles Talis <gilles.talis@gmail.com>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>

package/pptp-linux/pptp-linux.mk

@@ -8,6 +8,8 @@ PPTP_LINUX_VERSION = 1.7.2
 PPTP_LINUX_SITE = http://downloads.sourceforge.net/project/pptpclient/pptp/pptp-$(PPTP_LINUX_VERSION)
 PPTP_LINUX_SOURCE = pptp-$(PPTP_LINUX_VERSION).tar.gz
 PPTP_LINUX_MAKE = $(MAKE1)
+PPTP_LINUX_LICENSE = GPLv2+
+PPTP_LINUX_LICENSE_FILES = COPYING
 
 define PPTP_LINUX_BUILD_CMDS
 	$(MAKE) -C $(@D) OPTIMIZE= DEBUG= \