added missing tests for Bug 55042: patch for missing function COMPLEX

git-svn-id: https://svn.apache.org/repos/asf/poi/trunk@1488808 13f79535-47bb-0310-9956-ffa450edef68
added missing tests for Bug 55042: patch for missing function COMPLEX

git-svn-id: https://svn.apache.org/repos/asf/poi/trunk@1488809 13f79535-47bb-0310-9956-ffa450edef68