Doxygen: exclude lib/plugins/
Doxygen: exclude lib/plugins/

This was the directory that caused me confusion in
d8822ca4ca255db1ce7a016e0461184342c474bd.

Tarsnap/tarsnap-gui,Tarsnap/tarsnap-gui,Tarsnap/tarsnap-gui,Tarsnap/tarsnap-gui,Tarsnap/tarsnap-gui