saned: fix [-Wunused-parameter] compiler warning

The `__sane_unused__` attribute has been moved from sanei_backend.h to
sanei.h to make it generally useful instead of limited to backends.

frontend/saned.c

@@ -3181,7 +3181,7 @@ run_standalone (char *user)
 
 
 static void
-run_inetd (char *sock)
+run_inetd (char __sane_unused__ *sock)
 {
   
   int fd = -1;

include/sane/sanei.h

@@ -92,6 +92,9 @@
 /** @name Public macros and functions
  * @{
  */
+/** @def __sane_unused__
+ * Mark parameters as potentially unused.
+ */
 /** @def STRINGIFY(x)
  * Turn parameter into string.
  */
@@ -137,6 +140,14 @@
 /* @} */
 
 /* A few convenience macros:  */
+
+/** @hideinitializer */
+#ifdef __GNUC__
+#define __sane_unused__ __attribute__((unused))
+#else
+#define __sane_unused__
+#endif
+
 /** @hideinitializer */
 #define NELEMS(a)	((int)(sizeof (a) / sizeof (a[0])))
 

include/sane/sanei_backend.h

@@ -9,20 +9,6 @@
  */
 
 
-/*
- * Compiler related options
- */
-
-/** Mark unused variables/parameters
- *
- * Tells the compiler a variable is unused, so the compiler doesn't spit a warning. 
- */
-#ifdef __GNUC__
-#define __sane_unused__ __attribute__((unused))
-#else
-#define __sane_unused__
-#endif
-
 /** @name Compatibility macros
  * @{
  */