keepalived: fix build with 4.15+ kernel headers

Kernel version 4.15 change the logic of libc-compat.h in a way that
introduced libc/kernel network headers collision. Add a patch for fixing
that.

Fixes:
http://autobuild.buildroot.net/results/000/000293275076c59e298d235e93ce9a92b66360e7/
http://autobuild.buildroot.net/results/2ba/2ba8722a42aa9b92f5194595f53130c97647b9b8/
http://autobuild.buildroot.net/results/114/114136447c9b18436ff9b2804c440a2e37576452/



Cc: Ilias Apalodimas <apalos@gmail.com>
Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>