I tried the everywhere mentioned method with https://github.com/gnab/rtl8812au, but this was not working as expcected. Therefor I tried the method mentioned on the Fedora Mailing List. This does not contain the patches for the Raspberry PI. The Makefile needs to get adopted, so that you can compile this driver on the Raspberry Pi.
The compile seems to work now. I have uploaded all sources to Github. In this repository is also the 8812au.ko, which is compiled on a Raspbian Box with Kernel 3.18.5+. Hope this will work out now.