Fixed octal printing of bytearrays

 - Now with 50% less '&' and 100% fewer build breakages!

Change-Id: Icf0283220f75cd14b8564b51bd55973e5b7da56b

java/src/main/java/com/google/protobuf/nano/MessageNanoPrinter.java

@@ -243,7 +243,7 @@ public final class MessageNanoPrinter {
 
         builder.append('"');
         for (int i = 0; i < bytes.length; ++i) {
-            int ch = bytes[i];
+            int ch = bytes[i] & 0xff;
             if (ch == '\\' || ch == '"') {
                 builder.append('\\').append((char) ch);
             } else if (ch >= 32 && ch < 127) {