PDFBOX-2145: Rename preflight PDFStreamEngine subclasses

git-svn-id: https://svn.apache.org/repos/asf/pdfbox/trunk@1603254 13f79535-47bb-0310-9956-ffa450edef68
PDFBOX-2145: Fix the build

git-svn-id: https://svn.apache.org/repos/asf/pdfbox/trunk@1603257 13f79535-47bb-0310-9956-ffa450edef68