IO-356 CharSequenceInputStream#reset() behaves incorrectly in case when buffer size is not dividable by data size.
       Fix code so skip relates to the encoded bytes; reset now re-encodes the data up to the point of the mark

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/io/trunk@1471209 13f79535-47bb-0310-9956-ffa450edef68