gnu: emacs-xelb: Fix compilation error with xcb-proto@1.15.

* gnu/packages/patches/emacs-xelb-ignore-length-element.patch: New file.
* gnu/local.mk (dist_patch_DATA): Add it.
* gnu/packages/emacs-xyz.scm (emacs-xelb): Use it.

gnu/local.mk

@@ -1077,6 +1077,7 @@ dist_patch_DATA =						\
   %D%/packages/patches/emacs-yasnippet-fix-tests.patch	\
   %D%/packages/patches/emacs-kv-fix-tests.patch	\
   %D%/packages/patches/emacs-pgtk-super-key-fix.patch	\
+  %D%/packages/patches/emacs-xelb-ignore-length-element.patch	\
   %D%/packages/patches/enjarify-setup-py.patch			\
   %D%/packages/patches/enlightenment-fix-setuid-path.patch	\
   %D%/packages/patches/erlang-man-path.patch			\

gnu/packages/emacs-xyz.scm

@@ -1,6 +1,6 @@
 ;;; GNU Guix --- Functional package management for GNU
 ;;; Copyright © 2014 Taylan Ulrich Bayirli/Kammer <taylanbayirli@gmail.com>
-;;; Copyright © 2013-2022 Ludovic Courtès <ludo@gnu.org>
+;;; Copyright © 2013-2023 Ludovic Courtès <ludo@gnu.org>
 ;;; Copyright © 2014, 2015, 2016, 2017, 2018 Mark H Weaver <mhw@netris.org>
 ;;; Copyright © 2014, 2015, 2016, 2017, 2018, 2019 Alex Kost <alezost@gmail.com>
 ;;; Copyright © 2015 Federico Beffa <beffa@fbengineering.ch>
@@ -17808,7 +17808,9 @@ conflicts.")
                                   version ".tar"))
               (sha256
                (base32
-                "1fp5mzl63sh0h3ws4l5p4qgvi7ny8a3fj6k4dhqa98xgw2bx03v7"))))
+                "1fp5mzl63sh0h3ws4l5p4qgvi7ny8a3fj6k4dhqa98xgw2bx03v7"))
+              (patches
+               (search-patches "emacs-xelb-ignore-length-element.patch"))))
     (build-system emacs-build-system)
     ;; The following functions and variables needed by emacs-xelb are
     ;; not included in emacs-minimal:

gnu/packages/patches/emacs-xelb-ignore-length-element.patch

@@ -0,0 +1,19 @@
+Work around build failure due to XCB "length" element.
+Patch from <https://sources.debian.org/patches/xelb/0.18-4/>.
+
+Author: Martin <debacle@debian.org>
+Bug: https://github.com/ch11ng/xelb/issues/28
+Bug-Debian: https://bugs.debian.org/1017294
+
+---
+--- a/el_client.el
++++ b/el_client.el
+@@ -519,7 +519,7 @@
+     (`list (xelb-parse-list node))
+     (`exprfield (xelb-parse-exprfield node))
+     (`switch (xelb-parse-switch node))
+-    ((or `comment `doc))                ;simply ignored
++    ((or `comment `doc `length))                ;simply ignored
+     (x (error "Unsupported structure content: <%s>" x))))
+ 
+ ;; The car of the result shall be renamed to prevent duplication of slot names