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='2021-02-07 16:37:24 +0200'>2021-02-07</span></td><td><a href='/guix/commit/gnu/packages/mastodon.scm?id=3311a7470a06b60a7124b7d80853a45d7dbd7713'>gnu: tootle: Update to 1.0.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/mastodon.scm (tootle): Update to 1.0.
</span></span></td><td>Efraim Flashner</td></tr>
<tr><td><span title='2021-02-03 10:14:53 +0200'>2021-02-03</span></td><td><a href='/guix/commit/gnu/packages/mastodon.scm?id=63cf277bfacf282d2b19f00553745b2a9370eca0'>gnu: Add tootle.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/mastodon.scm (tootle): New variable.
</span></span></td><td>Efraim Flashner</td></tr>
<tr><td><span title='2020-07-27 13:11:37 +0300'>2020-07-27</span></td><td><a href='/guix/commit/gnu/packages/mastodon.scm?id=069da2433e429a6b9b2a0d2a4bea40418d465c4d'>gnu: Add python-mastodon-py.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/mastodon.scm (python-mastodon-py): New variable.
</span></span></td><td>Efraim Flashner</td></tr>