Support for Hurd and other non-linux GNU systems.

Non-linux GNU systems such as Hurd will define __GLIBC__ or __GNU__
rather than __linux__.  This must be tested for in order to get byteswap.h
included.  See commit 594d180 (24 Dec
2006) and other related patches (fixed in upstream HEAD then, why was
the patch not brought across to the 1.3 branch?).

GL/glx/indirect_dispatch_swap.c

@@ -28,7 +28,7 @@
 #include <X11/Xmd.h>
 #include <GL/gl.h>
 #include <GL/glxproto.h>
-#ifdef __linux__
+#if defined(__linux__) || defined (__GLIBC__) || defined(__GNU__)
 #include <byteswap.h>
 #elif defined(__OpenBSD__)
 #include <sys/endian.h>

GL/glx/indirect_program.c

@@ -46,7 +46,7 @@
 #include "dispatch.h"
 #include "glapioffsets.h"
 
-#ifdef __linux__
+#if defined(__linux__) || defined (__GLIBC__) || defined(__GNU__)
 #include <byteswap.h>
 #elif defined(__OpenBSD__)
 #include <sys/endian.h>

GL/glx/indirect_texture_compression.c

@@ -39,7 +39,7 @@
 #include "glthread.h"
 #include "dispatch.h"
 
-#ifdef __linux__
+#if defined(__linux__) || defined (__GLIBC__) || defined(__GNU__)
 #include <byteswap.h>
 #elif defined(__OpenBSD__)
 #include <sys/endian.h>

GL/glx/swap_interval.c

@@ -40,7 +40,7 @@
 #include "dispatch.h"
 #include "glapioffsets.h"
 
-#ifdef __linux__
+#if defined(__linux__) || defined (__GLIBC__) || defined(__GNU__)
 #include <byteswap.h>
 #elif defined(__OpenBSD__)
 #include <sys/endian.h>