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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<div class='path'>path: <a href='/guix/log/?id=b3679394ec5a703de957e4344d2e20b7e306cd39'>root</a>/<a href='/guix/log/tests?id=b3679394ec5a703de957e4344d2e20b7e306cd39'>tests</a>/<a href='/guix/log/tests/zlib.scm?id=b3679394ec5a703de957e4344d2e20b7e306cd39'>zlib.scm</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/zlib.scm?id=b3679394ec5a703de957e4344d2e20b7e306cd39&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2019-04-16 17:30:22 +0200'>2019-04-16</span></td><td><a href='/guix/commit/tests/zlib.scm?id=b2c3640d2baa7bc929bf21880e6fb2785f5997f6'>tests: Gracefully skip zlib test when zlib is missing.</a><span class='msg-avail'>...<span class='msg-tooltip'>* tests/zlib.scm: Use 'test-skip' instead of (exit 77)
when (zlib-available?) returns false.
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2017-10-11 15:20:50 +0200'>2017-10-11</span></td><td><a href='/guix/commit/tests/zlib.scm?id=85a2b58987bc32e33e63bea86c1a94496b796ae9'>zlib: Fix memory leak due to revealed ports not being GC'd.</a><span class='msg-avail'>...<span class='msg-tooltip'>Fixes &lt;https://bugs.gnu.org/28784&gt;.

This mostly reverts 81a0f1cdf12e7bcc34c1203f034a323fa8f52cf5, which
introduced a regression: revealed ports are *never* GC'd (contrary to
what Guile's manual suggests).

In addition to the revert, 'close-procedure' now explicitly swallows
EBADF errors when 'close-port' is called.

* guix/zlib.scm (close-procedure): New procedure.
(make-gzip-input-port)[gzfile]: Use 'fileno' instead of 'port-&gt;fdes'.
Use 'close-procedure' instead of 'gzclose'.
(make-gzip-output-port): Likewise.
* tests/zlib.scm ("compression/decompression pipe"): Use 'port-closed?'
to determine whether PARENT has been closed.
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2017-03-15 15:19:53 +0100'>2017-03-15</span></td><td><a href='/guix/commit/tests/zlib.scm?id=81a0f1cdf12e7bcc34c1203f034a323fa8f52cf5'>zlib: Don't rely on EBADF being ignored by 'fport_close'.</a><span class='msg-avail'>...<span class='msg-tooltip'>In 2.2, 'fport_close' no longer swallows EBADF and instead raises a
'system-error' for this.  This commit adjusts for 2.2.

* guix/zlib.scm (close-procedure): Remove.
(make-gzip-input-port): Use 'port-&gt;fdes' instead of 'fileno'.
Use 'gzclose' instead of 'close-procedure'.
(make-gzip-output-port): Likewise.
* tests/zlib.scm ("compression/decompression pipe"): Don't check whether
PARENT is closed using 'port-closed?'.  Instead, use 'seek' on the
underlying FD and check for EBADF.
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2016-07-19 00:07:12 +0200'>2016-07-19</span></td><td><a href='/guix/commit/tests/zlib.scm?id=721539026dda02e58addbb618f2102b31a2927f8'>Add (guix zlib).</a><span class='msg-avail'>...<span class='msg-tooltip'>* guix/zlib.scm, tests/zlib.scm: New files.
* Makefile.am (MODULES): Add guix/zlib.scm.
(SCM_TESTS): Add tests/zlib.scm.
* m4/guix.m4 (GUIX_LIBGCRYPT_LIBDIR): New macro.
* configure.ac (LIBGCRYPT_LIBDIR): Use it.  Define and substitute
'LIBZ'.
* guix/config.scm.in (%libz): New variable.
</span></span></td><td>Ludovic Courtès</td></tr>