Fix bug in Int31.shift_right_logical

Author: OlivierNicole

compiler/lib/stdlib.ml

@@ -447,8 +447,7 @@ end = struct
 
   let shift_right = shift_op Int32.shift_right
 
-  let shift_right_logical a b =
-    shift_op Int32.shift_right_logical (Int32.logand a 0x7fffffffl) b
+  let shift_right_logical a b = shift_op Int32.shift_right_logical a b
 
   let to_int32 (x : t) : int32 = x
 end