tmux: Add KERN_PROC_CWD support on NetBSD

If KERN_PROC_CWD is available use it instead of using procfs.

PKGREVISION++

Index: Makefile
===================================================================
RCS file: /cvsroot/pkgsrc/misc/tmux/Makefile,v
retrieving revision 1.48
diff -u -p -r1.48 Makefile
--- Makefile	3 May 2019 10:49:35 -0000	1.48
+++ Makefile	14 Jun 2019 20:07:14 -0000
@@ -1,6 +1,7 @@
 # $NetBSD: Makefile,v 1.48 2019/05/03 10:49:35 triaxx Exp $
 
 DISTNAME=	tmux-2.9a
+PKGREVISION=	1
 CATEGORIES=	misc
 MASTER_SITES=	${MASTER_SITE_GITHUB:=tmux/}
 GITHUB_RELEASE=	${PKGVERSION_NOREV}
Index: distinfo
===================================================================
RCS file: /cvsroot/pkgsrc/misc/tmux/distinfo,v
retrieving revision 1.40
diff -u -p -r1.40 distinfo
--- distinfo	3 May 2019 10:49:35 -0000	1.40
+++ distinfo	14 Jun 2019 20:07:14 -0000
@@ -4,3 +4,4 @@ SHA1 (tmux-2.9a.tar.gz) = 33cba73e64c62f
 RMD160 (tmux-2.9a.tar.gz) = e5460971073abb865adcea2a6711e82d84c53838
 SHA512 (tmux-2.9a.tar.gz) = aca6882688727c10c5647443fdd18bbd6c0f80b7a3bf9667903d1b89d523e604cd715f176f33f2e5673258f00e626a6dc273f80fe97ae4f91621814d89985713
 Size (tmux-2.9a.tar.gz) = 510915 bytes
+SHA1 (patch-osdep-netbsd.c) = 90d335b544dbacc3860cfa6c13ecd61b11f09f30
Index: patches/patch-osdep-netbsd.c
===================================================================
RCS file: patches/patch-osdep-netbsd.c
diff -N patches/patch-osdep-netbsd.c
--- /dev/null	1 Jan 1970 00:00:00 -0000
+++ patches/patch-osdep-netbsd.c	14 Jun 2019 20:07:14 -0000
@@ -0,0 +1,40 @@
+$NetBSD$
+
+Add support for KERN_PROC_CWD.
+
+--- osdep-netbsd.c.orig	2019-03-26 14:34:58.000000000 +0000
++++ osdep-netbsd.c
+@@ -135,11 +135,24 @@ osdep_get_cwd(int fd)
+ 	static char	target[PATH_MAX + 1];
+ 	char		*path;
+ 	pid_t		pgrp;
+-	ssize_t		n;
+ 
+ 	if ((pgrp = tcgetpgrp(fd)) == -1)
+ 		return (NULL);
+ 
++#ifdef KERN_PROC_CWD
++	int		mib[4];
++	size_t		len;
++
++	mib[0] = CTL_KERN;
++	mib[1] = KERN_PROC_ARGS;
++	mib[2] = pgrp;
++	mib[3] = KERN_PROC_CWD;
++	len = sizeof(target);
++	if (sysctl(mib, 4, target, &len, NULL, 0) == 0)
++		return (target);
++#else
++	ssize_t		n;
++
+ 	xasprintf(&path, "/proc/%lld/cwd", (long long) pgrp);
+ 	n = readlink(path, target, sizeof(target) - 1);
+ 	free(path);
+@@ -147,6 +160,7 @@ osdep_get_cwd(int fd)
+ 		target[n] = '\0';
+ 		return (target);
+ 	}
++#endif
+ 
+ 	return (NULL);
+ }