Update to upstream version 0.21.6

Details:
- Mostly bugfix release, including seek fixes for opus and
  a use-after-free bug in playlist and flac files.
- Upstream changelog see:
  https://raw.githubusercontent.com/MusicPlayerDaemon/MPD/v0.21.6/NEWS

MFH:		2019Q1

audio/musicpd/Makefile

@@ -1,8 +1,7 @@
 # $FreeBSD$
 
 PORTNAME=	musicpd
-PORTVERSION=	0.21.5
-PORTREVISION=	1
+PORTVERSION=	0.21.6
 CATEGORIES=	audio ipv6
 MASTER_SITES=	https://www.musicpd.org/download/mpd/${PORTVERSION:R}/
 DISTNAME=	mpd-${PORTVERSION}

audio/musicpd/distinfo

@@ -1,3 +1,3 @@
-TIMESTAMP = 1550922923
-SHA256 (mpd-0.21.5.tar.xz) = 2ea9f0eb3a7bdae5d705adf4e8ec45ef38b5b9ddf133f32b8926dd4e205b0ef9
-SIZE (mpd-0.21.5.tar.xz) = 667624
+TIMESTAMP = 1553120841
+SHA256 (mpd-0.21.6.tar.xz) = 8d4d116acc069872ba68741016d284885e93f8558a88d0c7ed246b8e1f40e59f
+SIZE (mpd-0.21.6.tar.xz) = 669272

audio/musicpd/files/patch-src_lib_cdio_Paranoia.hxx

@@ -1,11 +0,0 @@
---- src/lib/cdio/Paranoia.hxx.orig	2019-02-22 14:23:33 UTC
-+++ src/lib/cdio/Paranoia.hxx
-@@ -43,6 +43,8 @@
- #include <stdexcept>
- #include <utility>
- 
-+#include <cstdio>
-+
- class CdromDrive {
- 	cdrom_drive_t *drv = nullptr;
-