Depreacte libGLw and dependent ports

Deprecate graphics/libGLw, and set expiration date.  libGLw has been
deprecated upstream.
Deprecate unowned and unmaintained ports that depend on libGLw:
graphics/inventor
science/xmakemol

Obtained from:	FreeBSD Graphics Team development repo
		https://github.com/FreeBSDDesktop/freebsd-ports/tree/feature/libGLw-deprecate

graphics/inventor/Makefile

@@ -15,6 +15,8 @@ COMMENT=	SGI's Open Inventor (TM)
 LICENSE=	LGPL21
 
 BROKEN=		unfetchable
+DEPRECATED=	Depends on expiring graphics/libGLw
+EXPIRATION_DATE=	2019-11-01
 
 ONLY_FOR_ARCHS=	amd64 i386
 CONFLICTS=	Coin-[0-9]* SoXt-[0-9]*

graphics/libGLw/Makefile

@@ -12,6 +12,9 @@ DIST_SUBDIR=	GL
 MAINTAINER=	x11@FreeBSD.org
 COMMENT=	OpenGL widgets library
 
+DEPRECATED=    Deprecated upstream
+EXPIRATION_DATE=       2019-11-01
+
 USES=		motif libtool pathfix pkgconfig tar:bzip2
 USE_LDCONFIG=	yes
 USE_GL=		gl

science/xmakemol/Makefile

@@ -10,6 +10,9 @@ MASTER_SITES=	SAVANNAH
 MAINTAINER=	ports@FreeBSD.org
 COMMENT=	Molecule Viewer Program Based on Motif Widget
 
+DEPRECATED=    Depends on expiring graphics/libGLw
+EXPIRATION_DATE=       2019-11-01
+
 USES=		gmake motif shebangfix
 USE_XORG=	xpm
 USE_GL=		glut glw