Fix internal error with Shift_Right operator on signed type

This is a regression present on the mainline and 10 branch in the form
of an ICE with a shift operator applied to a variable of a signed type,
and which is caused by a type mismatch.

gcc/ada/ChangeLog:
	* gcc-interface/trans.c (gnat_to_gnu) <N_Op_Shift>: Also convert
	GNU_MAX_SHIFT if the type of the operation has been changed.
	* gcc-interface/utils.c (can_materialize_object_renaming_p): Add
	pair of missing parentheses.

gcc/testsuite/ChangeLog:
	* gnat.dg/shift1.adb: New test.

gcc/ada/gcc-interface/trans.c

@@ -7085,6 +7085,8 @@ gnat_to_gnu (Node_Id gnat_node)
 	    if (TREE_CODE (gnu_lhs) == INTEGER_CST && ignore_lhs_overflow)
 	      TREE_OVERFLOW (gnu_lhs) = TREE_OVERFLOW (gnu_old_lhs);
 	    gnu_rhs = convert (gnu_type, gnu_rhs);
+	    if (gnu_max_shift)
+	      gnu_max_shift = convert (gnu_type, gnu_max_shift);
 	  }
 
 	/* For signed integer addition, subtraction and multiplication, do an

gcc/ada/gcc-interface/utils.c

@@ -5837,7 +5837,7 @@ can_materialize_object_renaming_p (Node_Id expr)
     {
       expr = Original_Node (expr);
 
-      switch Nkind (expr)
+      switch (Nkind (expr))
 	{
 	case N_Identifier:
 	case N_Expanded_Name:

gcc/testsuite/gnat.dg/shift1.adb

@@ -0,0 +1,15 @@
+-- { dg-do compile }
+-- { dg-options "-gnatws" }
+
+procedure Shift1 is
+
+  type T_Integer_8 is range -2 ** 7 .. 2 ** 7 - 1
+    with Size => 8;
+
+  pragma Provide_Shift_Operators (T_Integer_8);
+
+  X : T_Integer_8;
+
+begin
+  X := Shift_Right (X, 1);
+end;