Fixes "multiple definition" errors when building with GCC 10+.

Based on <https://bugs.gentoo.org/show_bug.cgi?id=706706>.
--- a/fig2dev/dev/gensvg.c	2010-07-01 22:41:16.000000000 +0200
+++ b/fig2dev/dev/gensvg.c	2022-02-27 20:02:33.379945500 +0100
@@ -230,10 +230,12 @@
 };
 
 /* arrowhead arrays */
-Point   points[50], fillpoints[50], clippoints[50];
-int     npoints, nfillpoints, nclippoints;
-int     arrowx1, arrowy1;	/* first point of object */
-int     arrowx2, arrowy2;	/* second point of object */
+Point   fillpoints[50];
+int     nfillpoints;
+extern Point   points[50], clippoints[50];
+extern int     npoints, nclippoints;
+extern int     arrowx1, arrowy1;	/* first point of object */
+extern int     arrowx2, arrowy2;	/* second point of object */
 
 static int tileno=0; /* number of current tile */ 
 
--- a/fig2dev/fig2dev.h	2010-03-16 19:53:20.000000000 +0100
+++ b/fig2dev/fig2dev.h	2022-02-27 19:56:06.072253991 +0100
@@ -126,7 +126,7 @@
 extern char	*prog, *from, *to;
 extern char	*name;
 extern double	font_size;
-Boolean	correct_font_size;	/* use correct font size */
+extern Boolean	correct_font_size;	/* use correct font size */
 extern double	mag, fontmag;
 extern FILE	*tfp;
 
/guix/tree/etc/substitutes?id=e68ae709093b7b5ab4bcca9a96c48c2df73e7212'>tree</a><a href='/guix/commit/etc/substitutes?id=e68ae709093b7b5ab4bcca9a96c48c2df73e7212'>commit</a><a href='/guix/diff/etc/substitutes?id=e68ae709093b7b5ab4bcca9a96c48c2df73e7212'>diff</a></td><td class='form'><form class='right' method='get' action='/guix/log/etc/substitutes'>
<input type='hidden' name='id' value='e68ae709093b7b5ab4bcca9a96c48c2df73e7212'/><select name='qt'>
<option value='grep'>log msg</option>
<option value='author'>author</option>
<option value='committer'>committer</option>
<option value='range'>range</option>
</select>
<input class='txt' type='search' size='10' name='q' value=''/>
<input type='submit' value='search'/>
</form>
</td></tr></table>
<div class='path'>path: <a href='/guix/log/?id=e68ae709093b7b5ab4bcca9a96c48c2df73e7212'>root</a>/<a href='/guix/log/etc?id=e68ae709093b7b5ab4bcca9a96c48c2df73e7212'>etc</a>/<a href='/guix/log/etc/substitutes?id=e68ae709093b7b5ab4bcca9a96c48c2df73e7212'>substitutes</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/etc/substitutes?id=e68ae709093b7b5ab4bcca9a96c48c2df73e7212&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2020-07-10 00:11:00 +0200'>2020-07-10</span></td><td><a href='/guix/commit/etc/substitutes?id=d283bb960f927dd5f7bb8b96bc697221e4e8ad39'>maint: Remove traces of "berlin.guixsd.org".</a><span class='msg-avail'>...<span class='msg-tooltip'>The guixsd.org domain is no longer advertised since before in 1.0.0
release in May 2019.

* etc/substitutes/berlin.guixsd.org.pub: Rename to...
* etc/substitutes/berlin.guix.gnu.org.pub: ... this.
* etc/substitutes/ci.guix.gnu.org.pub,
etc/substitutes/ci.guix.info.pub: Adjust accordingly.
* gnu/services/base.scm (%default-authorized-guix-keys): Likewise.
* guix/build/download-nar.scm (urls-for-item): Likewise.
* guix/self.scm (miscellaneous-files): Likewise.
* Makefile.am (dist_pkgdata_DATA): Likewise.
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2019-06-29 14:27:22 +0200'>2019-06-29</span></td><td><a href='/guix/commit/etc/substitutes?id=3a8bfebed94ba295432da8304b7ffb4a611ef761'>etc: Remove hydra.gnu.org.pub key.</a><span class='msg-avail'>...<span class='msg-tooltip'>* etc/substitutes/hydra.gnu.org.pub: Delete file.
* guix/self.scm (miscellaneous-files): Don't install it.
* Makefile.am (dist_pkgdata_DATA): Remove it.
* gnu/services/base.scm (%default-authorized-guix-keys): Likewise.
(hydra-key-authorization): Rename to…
(substitute-key-authorization): …this.  Adjust only call site.
</span></span></td><td>Tobias Geerinckx-Rice</td></tr>
<tr><td><span title='2019-05-01 11:05:47 +0200'>2019-05-01</span></td><td><a href='/guix/commit/etc/substitutes?id=757e633d57a7b994759d69e41dd759a39f1a34ae'>build: Change default substitute server to "ci.guix.gnu.org".</a><span class='msg-avail'>...<span class='msg-tooltip'>* config-daemon.ac: Replace "ci.guix.info" with "ci.guix.gnu.org".
* doc/guix.texi (SUBSTITUTE-SERVER): Likewise.
* etc/substitutes/ci.guix.gnu.org.pub: New file.
* Makefile.am (dist_pkgdata_DATA): Add it.
* guix/scripts/build.scm (%default-log-urls): Update.
* guix/scripts/substitute.scm (%default-substitute-urls): Likewise.
* guix/store.scm (%default-substitute-urls): Likewise.
* guix/self.scm (miscellaneous-files): Add "ci.guix.gnu.org".
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2018-12-04 10:57:56 +0100'>2018-12-04</span></td><td><a href='/guix/commit/etc/substitutes?id=6a837b6062ab405f6ca6d9c0163836769098d89b'>etc: Add "ci.guix.info.pub" public key file.</a><span class='msg-avail'>...<span class='msg-tooltip'>* etc/substitutes/ci.guix.info.pub: New file.
* Makefile.am (dist_pkgdata_DATA): Add it.
* guix/self.scm (miscellaneous-files): Add
"share/guix/ci.guix.info.pub".
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2018-11-06 00:04:11 +0100'>2018-11-06</span></td><td><a href='/guix/commit/etc/substitutes?id=aa919fbc890c5438166083f9ff02e4b1968a182b'>maint: Move substitute public keys to etc/substitutes.</a><span class='msg-avail'>...<span class='msg-tooltip'>* berlin.guixsd.org.pub, hydra.gnu.org.pub: Move to...
* etc/substitutes: ... here.  New directory.
* Makefile.am (dist_pkgdata_DATA): Adjust accordingly.
</span></span></td><td>Ludovic Courtès</td></tr>