Fixes compilation with Mesa >= 18.2.5.

Taken from upstream:

https://github.com/liballeg/allegro5/commit/a40d30e21802ecf5c9382cf34af9b01bd3781e47

diff --git a/include/allegro5/allegro_opengl.h b/include/allegro5/allegro_opengl.h
index 0f86a6768..652dd024e 100644
--- a/include/allegro5/allegro_opengl.h
+++ b/include/allegro5/allegro_opengl.h
@@ -103,10 +103,14 @@

 /* HACK: Prevent both Mesa and SGI's broken headers from screwing us */
 #define __glext_h_
+#define __gl_glext_h_
 #define __glxext_h_
+#define __glx_glxext_h_
 #include <GL/gl.h>
 #undef  __glext_h_
+#undef  __gl_glext_h_
 #undef  __glxext_h_
+#undef  __glx_glxext_h_

 #endif /* ALLEGRO_MACOSX */

diff --git a/include/allegro5/opengl/GLext/glx_ext_defs.h b/include/allegro5/opengl/GLext/glx_ext_defs.h
index 49c502091..fba8aea5d 100644
--- a/include/allegro5/opengl/GLext/glx_ext_defs.h
+++ b/include/allegro5/opengl/GLext/glx_ext_defs.h
@@ -1,7 +1,9 @@
 /* HACK: Prevent both Mesa and SGI's broken headers from screwing us */
 #define __glxext_h_
+#define __glx_glxext_h_
 #include <GL/glx.h>
 #undef __glxext_h_
+#undef __glx_glxext_h_

 #ifndef GLX_VERSION_1_3
 #define _ALLEGRO_GLX_VERSION_1_3
--
2.20.0
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<div class='path'>path: <a href='/guix/log/?id=0bca6c03098fba7f98b7050badd52f783b3dff0c&amp;showmsg=1'>root</a>/<a href='/guix/log/tests?id=0bca6c03098fba7f98b7050badd52f783b3dff0c&amp;showmsg=1'>tests</a>/<a href='/guix/log/tests/builders.scm?id=0bca6c03098fba7f98b7050badd52f783b3dff0c&amp;showmsg=1'>builders.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/builders.scm?id=0bca6c03098fba7f98b7050badd52f783b3dff0c'>Collapse</a>)</th><th class='left'>Author</th></tr>
<tr class='logheader'><td><span title='2023-09-26 17:36:58 +0200'>2023-09-26</span></td><td class='logsubject'><a href='/guix/commit/tests/builders.scm?id=13b0cf85eb31e1b1ea674debbbfb0f35a32d1374'>git-download: Use “builtin:git-download” when available.</a></td><td>Ludovic Courtès</td></tr>
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Fixes &lt;https://issues.guix.gnu.org/63331&gt;.

Longer-term this will remove Git from the derivation graph when its sole
use is to perform a checkout for a fixed-output derivation, thereby
breaking dependency cycles that can arise in these situations.

* guix/git-download.scm (git-fetch): Rename to…
(git-fetch/in-band): … this.  Deal with GIT or GUILE being #f.
(git-fetch/built-in, built-in-builders*, git-fetch): New procedures.
* tests/builders.scm ("git-fetch, file URI"): New test.


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