Compiling-Instructions for macos

[LukasSchulz]

Not really an issue, because I found the solution, but when trying to build on MacOS, the build failes, because MacOS doesn't have sys/sendfile.h.

I was still able to compile sturmflut aufter replacing sys/sendfile.hwith importing sys/types.h, sys/socket.h and sys/uio.h.
I haven't looked much into the code, so I don't know which of those three are really necessary, but it does work on MacOS now.

[TobleMiner]

Cool! Thanks for the pointers towards MacOS compatibility. I'll leave this issue open, such that I remember to have a closer look at this some time in the future.