Fix for SVN 1.9.x 'nonexistent' for new files when relocation info is present.
When support for SVN 1.9 and its 'nonexistent' terminology for new

files was added, it did not include support for relocation info to be

present in diff headers. Hence if a patch file had a file that was

new with relocation info, ReviewBoard would reject the patch file as

malformatted. This fixes that, adding the relocation information

matching pattern to the nonexistent regexp.
Such a diff header that was causing problems before but is now accepted:

Index: new-file
===================================================================
--- new-file    (.../top-level-branch/doc)    (nonexistent)
+++ new-file    (.../branches/branch1/doc)    (revision 11)


Original reported at: https://hellosplat.com/s/beanbag/tickets/4374/

Using the testdata/svn_repo, created two diffs with SVN 1.9.4 that had 

new files, only one that had relocation info. Verified that after these

changes both patches were accepted as valid (before the changes the 

patch with relation info was NOT accepted).