Fix regression caused by fix for CVE-2016-0718 when building with -DXML_UNICODE.

Discussion:

https://sourceforge.net/p/expat/bugs/539/

Patch copied from upstream source repository:

https://sourceforge.net/p/expat/code_git/ci/af507cef2c93cb8d40062a0abe43a4f4e9158fb2/

From af507cef2c93cb8d40062a0abe43a4f4e9158fb2 Mon Sep 17 00:00:00 2001
From: Sebastian Pipping <sebastian@pipping.org>
Date: Sun, 17 Jul 2016 20:22:29 +0200
Subject: [PATCH 1/2] Fix regression bug #539 (needs -DXML_UNICODE)

Thanks to Andy Wang and Karl Waclawek!
---
 expat/lib/xmlparse.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/expat/lib/xmlparse.c b/expat/lib/xmlparse.c
index b308e67..0d5dd7b 100644
--- a/lib/xmlparse.c
+++ b/lib/xmlparse.c
@@ -2468,7 +2468,7 @@ doContent(XML_Parser parser,
                        &fromPtr, rawNameEnd,
                        (ICHAR **)&toPtr, (ICHAR *)tag->bufEnd - 1);
             convLen = (int)(toPtr - (XML_Char *)tag->buf);
-            if ((convert_res == XML_CONVERT_COMPLETED) || (convert_res == XML_CONVERT_INPUT_INCOMPLETE)) {
+            if ((fromPtr >= rawNameEnd) || (convert_res == XML_CONVERT_INPUT_INCOMPLETE)) {
               tag->name.strLen = convLen;
               break;
             }
-- 
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<tr><td><span title='2021-05-13 00:32:23 +0200'>2021-05-13</span></td><td><a href='/guix/commit/gnu/packages/webkit.scm?id=121b9354a2e5cb669c577b6a2535882c431a8d44'>gnu: webkitgtk: Update to 2.32.1.</a><span class='msg-avail'>...</span></td><td>Tobias Geerinckx-Rice</td></tr>
<tr><td><span title='2021-04-27 12:26:17 +0200'>2021-04-27</span></td><td><a href='/guix/commit/gnu/packages/webkit.scm?id=e5c65fb7372e10a2d6531d25f3b7d7c31679a21e'>gnu: webkitgtk: Always use at least 2 make jobs.</a><span class='msg-avail'>...</span></td><td>Tobias Geerinckx-Rice</td></tr>
<tr><td><span title='2021-03-30 14:11:28 -0400'>2021-03-30</span></td><td><a href='/guix/commit/gnu/packages/webkit.scm?id=3c5e1412e3ef769df8e4826d0aedabaa3aa0d631'>gnu: WebKitGTK: Update to 2.32.0 [fixes CVE-2021-{1788,1844,1871}].</a><span class='msg-avail'>...</span></td><td>Leo Famulari</td></tr>
<tr><td><span title='2021-03-27 19:48:50 -0400'>2021-03-27</span></td><td><a href='/guix/commit/gnu/packages/webkit.scm?id=9dea1618755891526f708aa335b4136c1302d16e'>gnu: Use 'gtk-doc/stable' in native-inputs of selected packages.</a><span class='msg-avail'>...</span></td><td>Mark H Weaver</td></tr>
<tr><td><span title='2021-03-21 22:13:32 +0100'>2021-03-21</span></td><td><a href='/guix/commit/gnu/packages/webkit.scm?id=759e9acd8f09e48ae20d4ee7985274d72331ccad'>gnu: webkitgtk: Update to 2.30.6.</a><span class='msg-avail'>...</span></td><td>Tobias Geerinckx-Rice</td></tr>
<tr><td><span title='2021-03-14 06:07:10 +0100'>2021-03-14</span></td><td><a href='/guix/commit/gnu/packages/webkit.scm?id=92d0949a268fe8479af5851d5bb3733e207a5c81'>gnu: webkitgtk: Enable WOFF2 support.</a><span class='msg-avail'>...</span></td><td>Léo Le Bouter</td></tr>
<tr><td><span title='2021-03-14 06:04:33 +0100'>2021-03-14</span></td><td><a href='/guix/commit/gnu/packages/webkit.scm?id=37b5e79154529efa9058c5d01c4f7826d532aa05'>gnu: wpewebkit: Update to 2.30.5 [security fixes].</a><span class='msg-avail'>...</span></td><td>Léo Le Bouter</td></tr>
<tr><td><span title='2021-02-16 17:54:07 -0500'>2021-02-16</span></td><td><a href='/guix/commit/gnu/packages/webkit.scm?id=8fc36d82271946bf5e327b0f2feef9f65ce91701'>gnu: WebKitGTK: Update to 2.30.5 [fixes CVE-2020-13558].</a><span class='msg-avail'>...</span></td><td>Leo Famulari</td></tr>