Standardization of method signatures.

backend/escl/escl_jpeg.c

@@ -188,6 +188,7 @@ get_JPEG_data(capabilities_t __sane_unused__ *scanner,
               int __sane_unused__ *h,
               int __sane_unused__ *bps)
 {
+    return (SANE_STATUS_INVAL);
 }
 
 #endif

backend/escl/escl_png.c

@@ -137,6 +137,7 @@ get_PNG_data(capabilities_t __sane_unused__ *scanner,
               int __sane_unused__ *h,
               int __sane_unused__ *bps)
 {
+    return (SANE_STATUS_INVAL);
 }
 
 #endif