irc/bitchx: some minor, non-functional changes to the port (+)

Update WWW line, GC no longer needed GNU_CONFIGURE_MANPREFIX, and
simplify the inference of --with-plugins configure switch value.

Try to remove MAKE_JOBS_UNSAFE (again): it was readded with commit
b6cc4b7085 because `chinese/bitchx' slave port was trying to
link `wserv' program before all of its object files were built.
Unfortunately, I could not find the build log from those days and
my attempts to force this error had failed.  The program is linked
from five object files and all of them are listed as the target's
dependencies.  Let's try to see the actual error if the bug could
still exhibit itself.

Reported on:	https://forums.freebsd.org/threads/irc.93538/post-656154
Forwarded by:	Graham Perrin

irc/bitchx/Makefile

@@ -7,21 +7,18 @@ MASTER_SITES=	SF/${PORTNAME}/ircii-pana/${PORTNAME}-${DISTVERSION}
 
 MAINTAINER=	danfe@FreeBSD.org
 COMMENT=	Feature-rich scriptable IRC client
-WWW=		http://www.bitchx.org/
+WWW=		https://bitchx.sourceforge.net/
 
 LICENSE=	BSD3CLAUSE
 LICENSE_FILE=	${WRKSRC}/COPYRIGHT
 
 USES=		cpe gmake ncurses
 GNU_CONFIGURE=	yes
-GNU_CONFIGURE_MANPREFIX=${PREFIX}/share
 CONFIGURE_ARGS=	--exec-prefix="${PREFIX}/share" \
 		--bindir="${PREFIX}/bin" \
 		--datadir="${PREFIX}/share" \
 		--libdir="${PREFIX}/share"
 
-MAKE_JOBS_UNSAFE=	yes
-
 CONFLICTS_INSTALL?=	zh-bitchx
 
 DATADIR=	${PREFIX}/share/bx
@@ -39,7 +36,7 @@ PLUGINS_DESC=	Build a handful of BitchX plugins
 TOGGLES_DESC=	Disable annoyance toggles
 
 IPV6_CONFIGURE_ENABLE=	ipv6
-PLUGINS_CONFIGURE_WITH=	plugins="${PLUGIN_LIST:C/\$$/,/g}"
+PLUGINS_CONFIGURE_WITH=	plugins="${PLUGIN_LIST:ts,}"
 SSL_USES=		ssl
 SSL_CONFIGURE_WITH=	ssl="${OPENSSLBASE}"