Bug#758896: witty: FTBFS on all buildds: fails to remove /usr/share/doc/libwt-doc/examples': Directory not empty

[Pau Garcia i Quiles]

I have now reproduced the issue.

It's caused by doxygen 1.8.8-3 leaving a stale doxygen_sqlite3.db file,
which 1.8.7 did not.

I have implemented a fix and the package is rebuilding.