Fix compiler warning in INIT/ratz.c (#28)

src/cmd/INIT/ratz.c:
- Fix build warning:

  src/cmd/INIT/ratz.c:4741:2: warning: case label value exceeds maximum value for
   type
   4741 |  case 0241:
        |  ^~~~

  The character literal in the switch expression was being treated
  as a signed char while the case label 0241 is greater than 127,
  resulting in this warning.

src/cmd/INIT/ratz.c

@@ -4736,7 +4736,7 @@ char**	argv;
 	}
 	else
 		state.id = "ratz";
-	switch ('~')
+	switch ((unsigned char)'~')
 	{
 	case 0241:
 		switch ('\n')