Replace int -> uint to avoid signed integer overflow

An example of such an error (should be compiled with DEBUG_SANITIZE):

runtime error: left shift of 1 by 31 places cannot be represented in
type 'int'

Signed-off-by: Rostislav Skudnov <rostislav@tuxera.com>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
diff --git a/libbb/getopt32.c b/libbb/getopt32.c
index 15b6efc..497fc01 100644
--- a/libbb/getopt32.c
+++ b/libbb/getopt32.c
@@ -404,7 +404,7 @@
 		if (c >= 32)
 			break;
 		on_off->opt_char = *s;
-		on_off->switch_on = (1 << c);
+		on_off->switch_on = (1U << c);
 		if (*++s == ':') {
 			on_off->optarg = va_arg(p, void **);
 			if (s[1] == '+' || s[1] == '*') {
@@ -454,7 +454,7 @@
 			if (c >= 32)
 				break;
 			on_off->opt_char = l_o->val;
-			on_off->switch_on = (1 << c);
+			on_off->switch_on = (1U << c);
 			if (l_o->has_arg != no_argument)
 				on_off->optarg = va_arg(p, void **);
 			c++;