private byte[] encodeStringbuilder(StringBuilder value) {
    byte[] b = encodeW1String(value.toString());
    b[0] = SPECIAL_STRINGBUILDER;
    return b;
  }
Handles old whalin (tested with v1.6) encoding: data type is in the first
byte of the value.

@author bpartensky
@since Oct 16, 2008
src/main/java/net/spy/memcached/transcoders/WhalinV1Transcoder.java