Fix struct fields order for SANE_Parameters to match actual standard and code.

html/doc012.html

@@ -360,10 +360,10 @@ typedef struct
   {
     SANE_Frame format;
     SANE_Bool last_frame;
+    SANE_Int bytes_per_line;
+    SANE_Int pixels_per_line;
     SANE_Int lines;
     SANE_Int depth;
-    SANE_Int pixels_per_line;
-    SANE_Int bytes_per_line;
   }
 SANE_Parameters;
 </pre>