Wireguard is not building on Fedora with 4.12 rc1 kernels

[Bruno Wolff III <bruno@wolff.to>]

It looks like the test for memneq is broken and both the kernel and compat 
versions get used at the same time.

[bruno@cerberus src]$ make
make -C /lib/modules/4.12.0-0.rc1.git0.1.fc27.x86_64/build M=/home/bruno/WireGuard/src modules
make[1]: Entering directory '/usr/src/kernels/4.12.0-0.rc1.git0.1.fc27.x86_64'
  CC [M]  /home/bruno/WireGuard/src/main.o
  CC [M]  /home/bruno/WireGuard/src/noise.o
In file included from /home/bruno/WireGuard/src/noise.c:15:0:
./include/crypto/algapi.h:389:19: error: redefinition of ‘crypto_memneq’
 static inline int crypto_memneq(const void *a, const void *b, size_t size)
                   ^~~~~~~~~~~~~
In file included from <command-line>:0:0:
/home/bruno/WireGuard/src/compat/memneq/include.h:2:19: note: previous definition of ‘crypto_memneq’ was here
 static inline int crypto_memneq(const void *a, const void *b, size_t size)
                   ^~~~~~~~~~~~~
make[2]: *** [scripts/Makefile.build:303: /home/bruno/WireGuard/src/noise.o] Error 1
make[1]: *** [Makefile:1516: _module_/home/bruno/WireGuard/src] Error 2
make[1]: Leaving directory '/usr/src/kernels/4.12.0-0.rc1.git0.1.fc27.x86_64'
make: *** [Makefile:28: module] Error 2