audio/lpac: Deprecate and set expiration date to 2021-12-31

Unfetchable and abandoned upstream in 2003
Reference: https://www.nue.tu-berlin.de/menue/mitarbeiterinnen/ehemalige_mitarbeiterinnen/tilman_liebchen/lpac_lossless_audio_codec_for_windows_and_linux/

PR:		258641
Approved by:	tcberner (mentor)
Differential Revision:	https://reviews.freebsd.org/D32041

audio/lpac/Makefile

@@ -16,6 +16,10 @@ LICENSE_NAME=	lpac
 LICENSE_TEXT=	No commercial use
 LICENSE_PERMS=	dist-mirror pkg-mirror auto-accept
 
+BROKEN=		Unfetchable
+DEPRECATED=	Abandoned upstream in 2003
+EXPIRATION_DATE=2021-12-31
+
 NO_BUILD=	yes
 USES=		linux
 PLIST_FILES=	bin/lpac