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='2022-10-23 14:40:32 +0200'>2022-10-23</span></td><td><a href='/guix/commit/gnu/packages/sdl.scm?id=083e6b209b8e5a3b54966efcf6f4142f3e9ac548'>gnu: guile-sdl2: Update to 0.8.0.</a><span class='msg-avail'>...</span></td><td>Liliana Marie Prikler</td></tr>
<tr><td><span title='2022-10-04 20:40:46 +0200'>2022-10-04</span></td><td><a href='/guix/commit/gnu/packages/sdl.scm?id=c264265abd7f0aa8d62c301dc22bc72cc2055b0e'>gnu: sdl2: Use ibus-minimal instead of ibus.</a><span class='msg-avail'>...</span></td><td>Liliana Marie Prikler</td></tr>
<tr><td><span title='2022-10-02 23:18:42 +0200'>2022-10-02</span></td><td><a href='/guix/commit/gnu/packages/sdl.scm?id=782c7455e1ea3785e8c7e9b300d55c9ebb441a35'>gnu: ffmpeg@4: Build against SDL2 2.0 so 'ffplay' gets built.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2022-09-13 00:20:33 -0400'>2022-09-13</span></td><td><a href='/guix/commit/gnu/packages/sdl.scm?id=f24bf279d41fab25ceb3fcc88bcd5da6fb1404ae'>gnu: sdl2: Update to 2.24.0, use gexps and remove input labels.</a><span class='msg-avail'>...</span></td><td>Maxim Cournoyer</td></tr>
<tr><td><span title='2022-09-01 19:08:12 -0400'>2022-09-01</span></td><td><a href='/guix/commit/gnu/packages/sdl.scm?id=bd638a8ad6140db87851a86faae89e736e148f3d'>gnu: Delete mono and dependent packages.</a><span class='msg-avail'>...</span></td><td>Maxim Cournoyer</td></tr>
<tr><td><span title='2022-09-01 16:05:12 +0300'>2022-09-01</span></td><td><a href='/guix/commit/gnu/packages/sdl.scm?id=f04325c92fa8b700619834500e1f3497ac9150b1'>bug#22020: [PATCH] gnu: guile-sdl: Update to 0.6.1.</a><span class='msg-avail'>...</span></td><td>Thiago Jung Bauermann</td></tr>