Fix compatibility with Qt 5.15.

Patch copied from upstream source repository:

https://bazaar.launchpad.net/~adamreichold/qpdfview/trunk/revision/2104

--- a/sources/model.h	2017-04-19 21:01:25 +0000
+++ b/sources/model.h	2020-06-09 06:24:11 +0000
@@ -24,6 +24,7 @@
 #define DOCUMENTMODEL_H
 
 #include <QList>
+#include <QPainterPath>
 #include <QtPlugin>
 #include <QWidget>
 #include <QVector>

s://git.koszko.org/cgit-static/cgit.png' alt='cgit logo'/></a></td>
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<input type='hidden' name='id' value='d9bb9f539093938c8b0ac9c204db990d5179e1d2'/><select name='h' onchange='this.form.submit();'>
<option value='koszko' selected='selected'>koszko</option>
<option value='koszko-scripts'>koszko-scripts</option>
</select> <input type='submit' value='switch'/></form></td></tr>
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<option value='author'>author</option>
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<input class='txt' type='search' size='10' name='q' value=''/>
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<div class='path'>path: <a href='/guix/log/?id=d9bb9f539093938c8b0ac9c204db990d5179e1d2'>root</a>/<a href='/guix/log/tests?id=d9bb9f539093938c8b0ac9c204db990d5179e1d2'>tests</a>/<a href='/guix/log/tests/guix-gc.sh?id=d9bb9f539093938c8b0ac9c204db990d5179e1d2'>guix-gc.sh</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/tests/guix-gc.sh?id=d9bb9f539093938c8b0ac9c204db990d5179e1d2&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2023-04-21 16:16:38 +0200'>2023-04-21</span></td><td><a href='/guix/commit/tests/guix-gc.sh?id=37dd69b44511dc73eb04bdebe8d82c9a0386338e'>tests: Fix checks for expected failures.</a><span class='msg-avail'>...<span class='msg-tooltip'>Addresses &lt;https://issues.guix.gnu.org/62406&gt;.

With 'set -e', a return status inverted with '!' does not cause the shell to
exit immediately.  Instead use '&amp;&amp; false' to indicate an expected failure.

* tests/guix-archive.sh, tests/guix-build-branch.sh, tests/guix-build.sh,
tests/guix-daemon.sh, tests/guix-download.sh,
tests/guix-environment-container.sh, tests/guix-environment.sh,
tests/guix-gc.sh, tests/guix-git-authenticate.sh, tests/guix-graph.sh,
tests/guix-hash.sh, tests/guix-home.sh, tests/guix-pack-relocatable.sh,
tests/guix-pack.sh, tests/guix-package-aliases.sh, tests/guix-package-net.sh,
tests/guix-package.sh, tests/guix-refresh.sh, tests/guix-shell.sh,
tests/guix-style.sh, tests/guix-system.sh: Replace uses of '! ...' with
'... &amp;&amp; false' or `test ! ...` as appropriate.

Signed-off-by: Ludovic Courtès &lt;ludo@gnu.org&gt;
</span></span></td><td>Eric Bavier</td></tr>