Use ifndef for V4L2 hacks

This should make life easier for *BSD support, and less error-prone on
Linux. Unfortunately, this does not work for enumerations.

modules/access/v4l2/v4l2.h

@@ -29,24 +29,29 @@
 #endif
 
 /* Hacks to compile with old headers */
-#ifdef __linux__
-# include <linux/version.h>
-# if LINUX_VERSION_CODE < KERNEL_VERSION(3,2,0)
+#ifndef V4L2_CTRL_FLAG_VOLATILE /* 3.2 */
 # warning Please update Video4Linux2 headers!
 # define V4L2_CTRL_FLAG_VOLATILE 0x0080
-# endif
+#endif
+#ifdef __linux__
+# include <linux/version.h>
 # if LINUX_VERSION_CODE < KERNEL_VERSION(3,1,0)
 #  define V4L2_CTRL_TYPE_BITMASK 8
 # endif
-# if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,35)
+#endif
+#ifndef V4L2_CID_ILLUMINATORS_1 /* 2.6.37 */
+# define V4L2_CID_ILLUMINATORS_1 (V4L2_CID_BASE+38)
+# define V4L2_CID_ILLUMINATORS_2 (V4L2_CID_BASE+37)
+#endif
+#ifndef V4L2_CID_CHROMA_GAIN /* 2.6.35 */
 # define V4L2_CID_CHROMA_GAIN (V4L2_CID_BASE+36)
-# endif
-# if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,33)
-#  define V4L2_CID_ROTATE (V4L2_CID_BASE+34)
+#endif
+#ifndef V4L2_CID_ROTATE /* 2.6.33 */
 # define V4L2_CID_BG_COLOR (V4L2_CID_BASE+35)
-# endif
+# define V4L2_CID_ROTATE (V4L2_CID_BASE+34)
 #endif
 
+
 #ifdef HAVE_LIBV4L2
 #   include <libv4l2.h>
 #else