Fix compatibility with libical 3.0.

Patch copied from Arch Linux:
https://git.archlinux.org/svntogit/packages.git/tree/trunk/gnome-todo-3.26.2-libical-3.0.patch?h=packages/gnome-todo

diff -up gnome-todo-3.26.2/src/gtd-task.c.libical-3.0 gnome-todo-3.26.2/src/gtd-task.c
--- gnome-todo-3.26.2/src/gtd-task.c.libical-3.0	2017-11-08 14:53:53.484294926 +0100
+++ gnome-todo-3.26.2/src/gtd-task.c	2017-11-08 14:53:57.208294874 +0100
@@ -778,7 +778,7 @@ gtd_task_set_complete (GtdTask  *task,
           dt->minute = g_date_time_get_minute (now);
           dt->second = g_date_time_get_seconds (now);
           dt->is_date = 0;
-          dt->is_utc = 1;
+          dt->zone = icaltimezone_get_utc_timezone ();
 
           /* convert timezone
            *
ted='selected'>koszko</option>
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<div class='path'>path: <a href='/guix/log/?id=d0308e68d6b26e95043415a3643adf15ae6725de'>root</a>/<a href='/guix/log/gnu?id=d0308e68d6b26e95043415a3643adf15ae6725de'>gnu</a>/<a href='/guix/log/gnu/packages?id=d0308e68d6b26e95043415a3643adf15ae6725de'>packages</a>/<a href='/guix/log/gnu/packages/esolangs.scm?id=d0308e68d6b26e95043415a3643adf15ae6725de'>esolangs.scm</a></div><div class='content'><table class='list nowrap'><tr class='nohover'><th class='left'>Age</th><th class='left'>Commit message (<a href='/guix/log/gnu/packages/esolangs.scm?id=d0308e68d6b26e95043415a3643adf15ae6725de&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2021-12-13 22:15:07 +0100'>2021-12-13</span></td><td><a href='/guix/commit/gnu/packages/esolangs.scm?id=e3196755e60ba7f1ed9d432e73f26a85e0c8893c'>gnu: Further simplify package inputs.</a><span class='msg-avail'>...<span class='msg-tooltip'>This is the result of running:

  ./pre-inst-env guix style --input-simplification=safe

and manually undoing changes on a dozen of packages to reduce
rebuilds (derivations for emacs, icecat, and libreoffice are unchanged.)
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2021-12-13 17:48:25 +0100'>2021-12-13</span></td><td><a href='/guix/commit/gnu/packages/esolangs.scm?id=8394619baceb118df92e355377fd543bb1aa501a'>gnu: Simplify package inputs.</a><span class='msg-avail'>...<span class='msg-tooltip'>This commit was obtained by running:

  ./pre-inst-env guix style

without any additional argument.
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2021-09-25 09:34:36 +0200'>2021-09-25</span></td><td><a href='/guix/commit/gnu/packages/esolangs.scm?id=719bbcc15e2216b59bde34f297b92ceb9d349ce0'>Update copyright assignments for Liliana Marie Prikler.</a><span class='msg-avail'>...<span class='msg-tooltip'>* doc/guix.texi: Update copyright name for Liliana Marie Prikler.
* gnu/packages/build-tools.scm: Update copyright name and email for Liliana
Marie Prikler.
* gnu/packages/convmv.scm: Likewise.
* gnu/packages/emacs-xyz.scm: Likewise.
* gnu/packages/emacs.scm: Likewise.
* gnu/packages/esolangs.scm: Likewise.
* gnu/packages/game-development.scm: Likewise.
* gnu/packages/games.scm: Likewise.
* gnu/packages/gnome-xyz.scm: Likewise.
* gnu/packages/gnome.scm: Likewise.
* gnu/packages/gstreamer.scm: Likewise.
* gnu/packages/guile-xyz.scm: Likewise.
* gnu/packages/minetest.scm: Likewise.
* gnu/packages/music.scm: Likewise.
* gnu/packages/patches/minetest-add-MINETEST_MOD_PATH.patch: Likewise.
* gnu/packages/patches/ppsspp-disable-upgrade-and-gold.patch: Likewise.
* gnu/packages/patches/webkitgtk-bind-all-fonts.patch: Likewise.
* gnu/packages/python-xyz.scm: Likewise.
* gnu/packages/unicode.scm: Likewise.
* gnu/packages/xorg.scm: Likewise.
* gnu/services/sound.scm: Likewise.
* guix/build-system/renpy.scm: Likewise.
* guix/build/emacs-utils.scm: Likewise.
* guix/build/renpy-build-system.scm: Likewise.
</span></span></td><td>Liliana Marie Prikler</td></tr>