Fix doc snarfing with GCC 4.5+.
From <http://git.savannah.gnu.org/cgit/guile.git/commit/?h=branch_release-1-8&id=aac41d28358cea594bb30f6e547afb82bb6004a6>.

diff --git a/scripts/snarf-check-and-output-texi b/scripts/snarf-check-and-output-texi
index ea33e17..8cd42e8 100755
--- a/scripts/snarf-check-and-output-texi
+++ b/scripts/snarf-check-and-output-texi
@@ -267,6 +267,17 @@ exec ${GUILE-guile} -l $0 -c "(apply $main (cdr (command-line)))" "$@"
       (set! *file* file)
       (set! *line* line))
 
+     ;; newer gccs like to throw around more location markers into the
+     ;; preprocessed source; these (hash . hash) bits are what they translate to
+     ;; in snarfy terms.
+     (('location ('string . file) ('int . line) ('hash . 'hash))
+      (set! *file* file)
+      (set! *line* line))
+
+     (('location ('hash . 'hash) ('string . file) ('int . line) ('hash . 'hash))
+      (set! *file* file)
+      (set! *line* line))
+
      (('arglist rest ...)
       (set! *args* (do-arglist rest)))
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<tr><td><span title='2021-03-08 00:06:43 +0100'>2021-03-08</span></td><td><a href='/guix/commit/gnu/packages/image-viewers.scm?id=2fa624ddd16c3a8c6180b441c8e9f520816225f6'>gnu: Add xzgv.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/image-viewers.scm (xzgv): New variable.

Signed-off-by: Nicolas Goaziou &lt;mail@nicolasgoaziou.fr&gt;
</span></span></td><td>Stefan Reichör</td></tr>
<tr><td><span title='2021-03-02 16:37:36 +0100'>2021-03-02</span></td><td><a href='/guix/commit/gnu/packages/image-viewers.scm?id=7bcbf35efa328456ece1b54426789501aed11b77'>gnu: feh: Update to 3.6.3.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/image-viewers.scm (feh): Update to 3.6.3.

Signed-off-by: Tobias Geerinckx-Rice &lt;me@tobias.gr&gt;
</span></span></td><td>Xinglu Chen</td></tr>
<tr><td><span title='2021-01-24 23:58:29 +0200'>2021-01-24</span></td><td><a href='/guix/commit/gnu/packages/image-viewers.scm?id=e330a31f7b7fd1542ce413e962ee36bef9fbc586'>gnu: catimg: Update to 2.7.0.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/image-viewers.scm (catimg): Update to 2.7.0.
</span></span></td><td>Efraim Flashner</td></tr>
<tr><td><span title='2021-01-09 23:14:26 +0100'>2021-01-09</span></td><td><a href='/guix/commit/gnu/packages/image-viewers.scm?id=65ba20e57f52313a4b0261917b84dd7cf925cec7'>gnu: feh: Update to 3.6.2.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/image-viewers.scm (feh): Update to 3.6.2.
</span></span></td><td>Tobias Geerinckx-Rice</td></tr>
<tr><td><span title='2021-01-05 22:46:53 +0200'>2021-01-05</span></td><td><a href='/guix/commit/gnu/packages/image-viewers.scm?id=08b12d0e5c0a000108712cc19e3d5e6242d7a086'>gnu: nomacs: Satisfy guix lint.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/image-viewers.scm (nomacs)[source]: Add file-name field.
[inputs]: Move qttools ...
[native-inputs]: ... to here.
</span></span></td><td>Efraim Flashner</td></tr>
<tr><td><span title='2021-01-04 15:06:04 +0100'>2021-01-04</span></td><td><a href='/guix/commit/gnu/packages/image-viewers.scm?id=08f35b9b6ca635f439bc2b01965aeb73e7ec282d'>gnu: Add nomacs photo lounge.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/image-viewers.scm (nomacs): New variable.

Signed-off-by: Leo Prikler &lt;leo.prikler@student.tugraz.at&gt;
</span></span></td><td>Rovanion Luckey</td></tr>
<tr><td><span title='2020-12-07 21:52:22 +0100'>2020-12-07</span></td><td><a href='/guix/commit/gnu/packages/image-viewers.scm?id=8c0d6a533a7d93222014934753515af77fd7162b'>gnu: feh: Update to 3.6.1.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/image-viewers.scm (feh): Update to 3.6.1.
</span></span></td><td>Tobias Geerinckx-Rice</td></tr>
<tr><td><span title='2020-12-01 20:55:42 +0100'>2020-12-01</span></td><td><a href='/guix/commit/gnu/packages/image-viewers.scm?id=8b7159ebbb5a57df63f26dd03b38800c5cd69702'>gnu: feh: Update to 3.6.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/image-viewers.scm (feh): Update to 3.6.
</span></span></td><td>Tobias Geerinckx-Rice</td></tr>
<tr><td><span title='2020-11-03 08:21:27 +0100'>2020-11-03</span></td><td><a href='/guix/commit/gnu/packages/image-viewers.scm?id=7a9e68cc8750a9b378ae54a42d3e882a2e548c95'>gnu: qview: Fix regexp.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/image-viewers.scm (qview): Fix regexps.
</span></span></td><td>Nicolas Goaziou</td></tr>
<tr><td><span title='2020-11-02 22:13:08 +0100'>2020-11-02</span></td><td><a href='/guix/commit/gnu/packages/image-viewers.scm?id=21df702808a8f4491e1ef5badc607748288fa69a'>gnu: qview: Update to 4.0.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/image-viewers.scm (qview): Update to 4.0.
[arguments]: Append PREFIX to qmake call.  Fix auto-update removal.
</span></span></td><td>Nicolas Goaziou</td></tr>