gnu: libvirt: Update to 5.6.0.

* gnu/packages/virtualization.scm (libvirt): Update to 5.6.0.
[source]: Remove patch.
* gnu/packages/patches/libvirt-remove-ATTRIBUTE_UNUSED.patch:
Delete file.
* gnu/local.mk (dist_patch_DATA): Remove it.

gnu/local.mk

@@ -1045,7 +1045,6 @@ dist_patch_DATA =						\
   %D%/packages/patches/libutils-add-includes.patch		\
   %D%/packages/patches/libutils-remove-damaging-includes.patch	\
   %D%/packages/patches/libvdpau-va-gl-unbundle.patch		\
-  %D%/packages/patches/libvirt-remove-ATTRIBUTE_UNUSED.patch	\
   %D%/packages/patches/libvpx-CVE-2016-2818.patch		\
   %D%/packages/patches/libvpx-use-after-free-in-postproc.patch	\
   %D%/packages/patches/libxslt-generated-ids.patch		\

gnu/packages/patches/libvirt-remove-ATTRIBUTE_UNUSED.patch

@@ -1,34 +0,0 @@
-From: Tobias Geerinckx-Rice <me@tobias.gr>
-Date: Thu, 25 Jul 2019 21:48:25 +0200
-Subject: [PATCH]: libvirt: remove ATTRIBUTE_UNUSED
-
-This should fix the error reported here[0].  Patch taken verbatim from
-upstream[1].
-
-[0]: https://debbugs.gnu.org/cgi/bugreport.cgi?bug=36634#28
-[1]: https://github.com/libvirt/libvirt/commit/759bf903a6c24a8efa25c7cf4b099d952eda9bd3
-
-From 759bf903a6c24a8efa25c7cf4b099d952eda9bd3 Mon Sep 17 00:00:00 2001
-From: Pavel Hrdina <phrdina@redhat.com>
-Date: Mon, 22 Jul 2019 14:46:34 +0200
-Subject: [PATCH] vircgroupv2: remove ATTRIBUTE_UNUSED for used attribute
-
-Signed-off-by: Pavel Hrdina <phrdina@redhat.com>
-Acked-by: Peter Krempa <pkrempa@redhat.com>
----
- src/util/vircgroupv2.c | 2 +-
- 1 file changed, 1 insertion(+), 1 deletion(-)
-
-diff --git a/src/util/vircgroupv2.c b/src/util/vircgroupv2.c
-index af3192c99c..e36c36685b 100644
---- a/src/util/vircgroupv2.c
-+++ b/src/util/vircgroupv2.c
-@@ -399,7 +399,7 @@ virCgroupV2EnableController(virCgroupPtr group,
- 
- 
- static int
--virCgroupV2MakeGroup(virCgroupPtr parent ATTRIBUTE_UNUSED,
-+virCgroupV2MakeGroup(virCgroupPtr parent,
-                      virCgroupPtr group,
-                      bool create,
-                      unsigned int flags)

gnu/packages/virtualization.scm

@@ -390,16 +390,14 @@ (define-public lxc
 (define-public libvirt
   (package
     (name "libvirt")
-    (version "5.5.0")
+    (version "5.6.0")
     (source
      (origin
        (method url-fetch)
        (uri (string-append "https://libvirt.org/sources/libvirt-"
                            version ".tar.xz"))
        (sha256
-        (base32 "1s1mzw4cmkcfivs1kphpgy4lpddx0w1qnjysr4ggk5558w4yy1i3"))
-       (patches
-        (search-patches "libvirt-remove-ATTRIBUTE_UNUSED.patch"))))
+        (base32 "1d5rmcx5fgb024hw8chbiv886n3jal5wp2yajjk5l4qh9s9gkx35"))))
     (build-system gnu-build-system)
     (arguments
      `(#:configure-flags