textproc/htdig: Fix build with Clang 6

In file included from Configuration.cc:24:
In file included from ./Configuration.h:107:
In file included from ./Dictionary.h:22:
./htString.h:28:10: fatal error: 'iostream.h' file not found
#include <iostream.h>
         ^~~~~~~~~~~~

http://beefy11.nyi.freebsd.org/data/head-i386-default/p477696_s338122/logs/errors/htdig-3.2.0.b6_6.log

- Fix WWW; htdig.org seems to be gone

textproc/htdig/Makefile

@@ -25,6 +25,7 @@ CONFIGURE_ARGS=	--with-config-dir=${PREFIX}/etc/htdig \
 		--with-image-url-prefix=/icons/htdig \
 		--with-ssl
 USES=		alias libtool ssl
+USE_CXXSTD=	c++98
 USE_LDCONFIG=	yes
 INSTALL_TARGET=	install-strip
 LDFLAGS+=	-L${OPENSSLLIB}

textproc/htdig/pkg-descr

@@ -8,4 +8,4 @@ single company, campus, or even a sub section of a web site.
 ht://Dig can span many web servers as long as they all understand
 the HTTP 1.0 protocol.
 
-WWW: http://www.htdig.org/
+WWW: https://sourceforge.net/projects/htdig/