Remove some compiler warnings.

backend/v4l-grab.h

@@ -33,7 +33,7 @@ struct GRABBER {
     struct STRTAB   *inputs;
 
     int   (*grab_open)(char *opt);
-    int   (*grab_close)();
+    int   (*grab_close)(void);
 
     int   (*grab_setupfb)(int sw, int sh, int format, void *base, int bpl);
     int   (*grab_overlay)(int x, int y, int width, int height, int format,
@@ -41,7 +41,7 @@ struct GRABBER {
 
     int   (*grab_setparams)(int format, int *width, int *height, int *linelength);
     void* (*grab_capture)(int single);
-    void  (*grab_cleanup)();
+    void  (*grab_cleanup)(void);
 
     int   (*grab_tune)(unsigned long freq);
     int   (*grab_tuned)(void);

backend/v4l.c

@@ -634,6 +634,8 @@ sane_get_devices (const SANE_Device *** device_list, SANE_Bool local_only)
   V4L_Device *dev;
   int i;
 
+  local_only = TRUE; /* Avoid compile warning */
+
   if (devlist)
     free (devlist);
 
@@ -1069,11 +1071,19 @@ sane_cancel (SANE_Handle handle)
 SANE_Status
 sane_set_io_mode (SANE_Handle handle, SANE_Bool non_blocking)
 {
+  /* Avoid compile warning */
+  handle = 0;
+  non_blocking = 0;
+
   return SANE_STATUS_UNSUPPORTED;
 }
 
 SANE_Status
 sane_get_select_fd (SANE_Handle handle, SANE_Int * fd)
 {
+  /* Avoid compile warning */
+  handle = 0;
+  fd = 0;
+
   return SANE_STATUS_UNSUPPORTED;
 }

backend/v4l.h

@@ -175,7 +175,7 @@ typedef struct V4L_Scanner
     Option_Value val[NUM_OPTIONS];
     V4L_Resolution resolution;
     SANE_Parameters params;
-    char* devicename;		/* Name of the Device */
+    SANE_String_Const devicename; /* Name of the Device */
     int fd;                     /* Filedescriptor */
     SANE_Int user_corner;       /* bitmask of user-selected coordinates */
     SANE_Int value_changed;     /* bitmask of options that were set */