Add net/tun to rump kernel src-netbsd

[huikang]

No description provided.

[huikang]

The changes to tests/[dynamic, ...]/Makefile are to fix the following compile error.

CC=/root/buildrump.sh/obj/tooldir/bin/x86_64--netbsd-gcc /root/buildrump.sh/obj/tooldir/bin/nbmkdep -s .o\ .ln\ .d -d -f .depend nettest_simple.d
#   compile  nettest_simple/nettest_simple.o
/root/buildrump.sh/obj/tooldir/bin/x86_64--netbsd-gcc -O2 -g -U_FORTIFY_SOURCE    -std=gnu99   -Werror    -I/root/buildrump.sh/tests/nettest_simple/../common -DRUMPUSER_CONFIG=yes -I/root/buildrump.sh/obj/tooldir/autoconf -I/root/buildrump.sh/obj/tooldir/compat/include -I/root/buildrump.sh/obj/dest.stage/usr/include   -c    /root/buildrump.sh/tests/nettest_simple/nettest_simple.c
#      link  nettest_simple/nettest_simple
/root/buildrump.sh/obj/tooldir/bin/x86_64--netbsd-gcc     -L/root/buildrump.sh/obj/dest.stage/usr/lib -Wl,-R/root/buildrump.sh/rump/lib -Wl,--no-as-needed     -o nettest_simple  nettest_simple.o  -Wl,--whole-archive -lrumpnet_shmif -lrumpnet_config -lrumpnet_netinet -lrumpnet_net -lrumpnet -lrumpkern_sysproxy -lrump -lrumpuser -Wl,--no-whole-archive -ldl  -lpthread    
/root/buildrump.sh/obj/dest.stage/usr/lib/librumpnet_net.so: undefined reference to `rumpns_config_cfdriver_attach'
collect2: error: ld returned 1 exit status

*** Failed target:  nettest_simple
*** Failed command: /root/buildrump.sh/obj/tooldir/bin/x86_64--netbsd-gcc -L/root/buildrump.sh/obj/dest.stage/usr/lib -Wl,-R/root/buildrump.sh/rump/lib -Wl,--no-as-needed -o nettest_simple nettest_simple.o -Wl,--whole-archive -lrumpnet_shmif -lrumpnet_config -lrumpnet_netinet -lrumpnet_net -lrumpnet -lrumpkern_sysproxy -lrump -lrumpuser -Wl,--no-whole-archive -ldl -lpthread 
*** Error code 1

[huikang]

Hi, @anttikantee please take a look at this PR when you have time. Thanks.