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='2023-07-30 02:00:00<tr><td><span title='2023-03-08 13:14:32 +0000'>2023-03-08</span></td><td><a href='/guix/commit/gnu/packages/skribilo.scm?id=85d4e8af5baf9b0a9cadf95d802674d0254433da'>gnu: skribilo: Update to 0.10.0.</a></td><td>Arun Isaac</td></tr>
:00:00 +0200'>2023-07-30</span></td><td><a href='/guix/commit/gnu/packages/entr.scm?id=e9abc417d3a284776bb2440c5d67a3bd4acb6a29'>gnu: entr: Update to 5.4.</a></td><td>Tobias Geerinckx-Rice</td></tr>
<tr><td><span title='2022-10-13 12:28:16 +0100'>2022-10-13</span></td><td><a href='/guix/commit/gnu/packages/entr.scm?id=10d429f2fce321d8285684503094694ec3979865'>gnu: entr: Update to 5.2.</a></td><td>jgart</td></tr>