Change from having actual zero bytes in java code to java-string notation for unicode-zero to avoid trouble with this file in Sonar when using PostgreSQL (which seems to fall over binary data in text files). The resulting test should be the same with the \u0000 notation

git-svn-id: https://svn.apache.org/repos/asf/poi/trunk@1532037 13f79535-47bb-0310-9956-ffa450edef68