Make the fix for net/if.h fuckup even worse (#3287)

Make the fix for net/if.h fuckup even worse (#3287)

The original conflict is fixed in the kernel in v4.6-rc7-40-g4a91cb61bb,
but now our work-around causes a compilation failure.
Keep the workaround to support 4.5 kernels for now, and layer
more ugliness on top.

Tested with:
kernel-headers-4.6.0-1.fc25.x86_64
glibc-devel-2.23.90-18.fc25.x86_64

kernel-headers-4.5.4-300.fc24.x86_64
glibc-devel-2.23.1-7.fc24.x86_64

kernel-headers-4.4.9-300.fc23.x86_64
glibc-devel-2.22-16.fc23.x86_64

kernel-headers-4.1.13-100.fc21.x86_64
glibc-devel-2.20-8.fc21.x86_64