PDFBOX-2503: don't ignore all trailing space alike characters, but NUL

git-svn-id: https://svn.apache.org/repos/asf/pdfbox/trunk@1640355 13f79535-47bb-0310-9956-ffa450edef68
PDFBOX-2503: added some test cases for metadata validation based on Maruans testfiles

git-svn-id: https://svn.apache.org/repos/asf/pdfbox/trunk@1640356 13f79535-47bb-0310-9956-ffa450edef68