Two patches to make it build

I tried packaging it as RPMs, I had two issues. One is that mono .dll files are not installed in libdir, the second is that the generate .cs files end up in generated/WebKit/*.cs etc so you need an extra */ in there.
This change will break compilation with gtk#  < 2.99.3. So when doing this change the required gtk# version would need to be bumped to 2.99.3