Provide interface to use SVN 1.8 diff output options (bug 476177)

https://bugs.eclipse.org/bugs/show_bug.cgi?id=476177

git-svn-id: https://dev.eclipse.org/svnroot/technology/org.eclipse.subversive/trunk@21502 ee007c2a-0a25-0410-9ab9-bf268980928c