Fixes compilation with Mesa >= 18.2.5.

Modified from upstream to work on allegro4:

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

diff --git a/addons/allegrogl/include/alleggl.h b/addons/allegrogl/include/alleggl.h
index 0f86a6768..652dd024e 100644
--- a/addons/allegrogl/include/alleggl.h
+++ b/addons/allegrogl/include/alleggl.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/addons/allegrogl/include/allegrogl/GLext/glx_ext_defs.h b/addons/allegrogl/include/allegrogl/GLext/glx_ext_defs.h
index 49c502091..fba8aea5d 100644
--- a/addons/allegrogl/include/allegrogl/GLext/glx_ext_defs.h
+++ b/addons/allegrogl/include/allegrogl/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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<tr><td><span title='2023-06-04 10:33:55 +0200'>2023-06-04</span></td><td><a href='/guix/commit/gnu/services/xorg.scm?id=f4f5ee6ad6e2432f52e37c549211df8f1cdbb571'>services: screen-locker-service-type: Configurable PAM and setuid.</a><span class='msg-avail'>...</span></td><td>muradm</td></tr>
<tr><td><span title='2023-05-11 13:21:45 +0200'>2023-05-11</span></td><td><a href='/guix/commit/gnu/services/xorg.scm?id=2df5d4fd18a2fbcb8066a50e2da8ec64635f5162'>system: pam: Let PAM extensions add shepherd requirements.</a><span class='msg-avail'>...</span></td><td>Josselin Poiret</td></tr>
<tr><td><span title='2023-03-25 10:06:36 +0800'>2023-03-25</span></td><td><a href='/guix/commit/gnu/services/xorg.scm?id=a7f118d062db4408b23505750c44a1f996496c43'>services: xorg-wrapper: Support xorg server input rewriting.</a><span class='msg-avail'>...</span></td><td>r0man</td></tr>
<tr><td><span title='2023-03-10 14:49:58 +0100'>2023-03-10</span></td><td><a href='/guix/commit/gnu/services/xorg.scm?id=5627c73a9e410c7e28d67df517bd275d8c5f5d8d'>services: xorg: Deprecate 'screen-locker-service' procedure.</a><span class='msg-avail'>...</span></td><td>Bruno Victal</td></tr>
<tr><td><span title='2022-11-18 15:44:39 +0100'>2022-11-18</span></td><td><a href='/guix/commit/gnu/services/xorg.scm?id=8d9647d8a77a67013c48166561134d92b5224264'>services: Add Shepherd 'configuration' action to various services.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2022-10-11 11:29:03 +0000'>2022-10-11</span></td><td><a href='/guix/commit/gnu/services/xorg.scm?id=683558e2ed8fd40ce29453b8136a95bedf55991a'>services: slim-service-type: Do not extend profile with xterm.</a><span class='msg-avail'>...</span></td><td>Maxim Cournoyer</td></tr>
<tr><td><span title='2022-10-07 10:11:13 -0400'>2022-10-07</span></td><td><a href='/guix/commit/gnu/services/xorg.scm?id=aad4e4fc6bed1209479970f1bcd2f08ee2b53d12'>services: xorg: Add auto-suspend? field to &lt;gdm-configuration&gt;.</a><span class='msg-avail'>...</span></td><td>Maxim Cournoyer</td></tr>
<tr><td><span title='2022-10-07 10:11:12 -0400'>2022-10-07</span></td><td><a href='/guix/commit/gnu/services/xorg.scm?id=7b896a26b8a911231d606b4fe664b03b95b27b39'>services: Add dconf-service-type.</a><span class='msg-avail'>...</span></td><td>Maxim Cournoyer</td></tr>
<tr><td><span title='2022-10-07 10:11:11 -0400'>2022-10-07</span></td><td><a href='/guix/commit/gnu/services/xorg.scm?id=1936668f5b7837104de4a091c8f6adf907ff9273'>services: gdm: Add a configuration field to enable XDMCP.</a><span class='msg-avail'>...</span></td><td>Maxim Cournoyer</td></tr>
<tr><td><span title='2022-09-16 16:27:08 -0400'>2022-09-16</span></td><td><a href='/guix/commit/gnu/services/xorg.scm?id=d7e56aebec4535f3567c362b6084818873e54b0d'>services: desktop: Mount /var/lib/gdm on a tmpfs file system.</a><span class='msg-avail'>...</span></td><td>Maxim Cournoyer</td></tr>
<tr><td><span title='2022-03-25 18:42:14 +0100'>2022-03-25</span></td><td><a href='/guix/commit/gnu/services/xorg.scm?id=2e55a4c6b9153fd1db60122cb29cee466693a753'>services: xorg: Remove xf86-input-synaptics from %default-xorg-modules.</a><span class='msg-avail'>...</span></td><td>SeerLite</td></tr>