Update to 3.1b.

Changes:	https://github.com/tmux/tmux/blob/3.1b/CHANGES

sysutils/tmux/Makefile

@@ -2,8 +2,7 @@
 # $FreeBSD$
 
 PORTNAME=	tmux
-PORTVERSION=	3.1a
-PORTREVISION=	1
+PORTVERSION=	3.1b
 CATEGORIES=	sysutils
 MASTER_SITES=	https://github.com/tmux/tmux/releases/download/${PORTVERSION}/
 DISTFILES=	${DISTNAME}${EXTRACT_SUFX}

sysutils/tmux/distinfo

-TIMESTAMP = 1588249694
-SHA256 (tmux-3.1a.tar.gz) = 10687cbb02082b8b9e076cf122f1b783acc2157be73021b4bedb47e958f4e484
-SIZE (tmux-3.1a.tar.gz) = 561121
+TIMESTAMP = 1589189119
+SHA256 (tmux-3.1b.tar.gz) = d93f351d50af05a75fe6681085670c786d9504a5da2608e481c47cf5e1486db9
+SIZE (tmux-3.1b.tar.gz) = 561152
 SHA256 (imomaliev-tmux-bash-completion-ef56d3e_GH0.tar.gz) = 2f8f3fe586bbdeec9b251ce3ef74f5edef19ba371968a8011acef860ddac59e1
 SIZE (imomaliev-tmux-bash-completion-ef56d3e_GH0.tar.gz) = 1526

sysutils/tmux/files/patch-6a33a12798b2afeee6fb7bba74d86d628137921e

-From 6a33a12798b2afeee6fb7bba74d86d628137921e Mon Sep 17 00:00:00 2001
-From: Nicholas Marriott <nicholas.marriott@gmail.com>
-Date: Thu, 30 Apr 2020 15:20:08 +0100
-Subject: [PATCH] Do not remove the automatic-rename option from the global
- set, only from the window (it must stay in the global set or tmux will
- crash). GitHub issue 2188.
-
---- input.c.orig	2020-04-29 20:01:18 UTC
-+++ input.c
-@@ -2304,7 +2304,7 @@ input_exit_rename(struct input_ctx *ictx)
- 		return;
- 
- 	if (ictx->input_len == 0) {
--		oe = options_get(wp->window->options, "automatic-rename");
-+		oe = options_get_only(wp->window->options, "automatic-rename");
- 		if (oe != NULL)
- 			options_remove(oe);
- 		return;