Fix erroneous cast from byte to int in IBBInputStream's read()

method. The casted value needs to be masked with 0xff, because bytes
in java are signed (two's complement)

Fixes SMACK-394

git-svn-id: http://svn.igniterealtime.org/svn/repos/smack/trunk@13387 b35dd754-fafc-0310-a699-88a17e54d16e

source/org/jivesoftware/smackx/bytestreams/ibb/InBandBytestreamSession.java

@@ -287,7 +287,7 @@ public class InBandBytestreamSession implements BytestreamSession {
             }
 
             // return byte and increment buffer pointer
-            return (int) buffer[bufferPointer++];
+            return ((int) buffer[bufferPointer++]) & 0xff;
         }
 
         public synchronized int read(byte[] b, int off, int len) throws IOException {