fix windows make install for html

[rurban]

html/
html/bin/
html/bin/.empty
html/ce-helpers/
html/ce-helpers/.empty
html/html/
html/html/lib/
html/html/lib/App/
html/html/lib/App/Prove/
html/html/lib/App/Prove/State/
html/html/lib/App/Prove/State/Result/
html/html/lib/App/Prove/State/Result/.empty
...
html/html/pod/
html/html/pod/.empty
html/include/
html/include/arpa/
html/include/arpa/.empty
html/include/sys/
html/include/sys/.empty
html/mini/
html/mini/.empty

All dirs are empty. html/html/ => html/ only lib and bin docs