multimedia/libmpeg2: Add missing license information

PR:		277017
Approved by:	tcberner (mentor), portmgr (blanket)

multimedia/libmpeg2/Makefile

@@ -1,6 +1,6 @@
 PORTNAME=	libmpeg2
 PORTVERSION=	0.5.1
-PORTREVISION=	7
+PORTREVISION=	8
 CATEGORIES=	multimedia
 MASTER_SITES=	http://libmpeg2.sourceforge.net/files/
 
@@ -8,6 +8,9 @@ MAINTAINER=	multimedia@FreeBSD.org
 COMMENT=	Free library for decoding MPEG-2 and MPEG-1 video streams
 WWW=		http://libmpeg2.sourceforge.net/
 
+LICENSE=	GPLv2+
+LICENSE_FILE=	${WRKSRC}/COPYING
+
 USES=		libtool pathfix
 GNU_CONFIGURE=	yes
 GNU_CONFIGURE_MANPREFIX=${PREFIX}/share