New package: badvpn

Comments are welcome.
```
cd /W/temporary/development/mingw-packages/mingw-w64-badvpn/src/build-x86_64/lwip && /D/applications/msys2.x64/mingw64/bin/gcc.exe    -pipe -shared -o liblwip.dll -Wl,--out-implib,liblwip.dll.a -Wl,--major-image-version,0,--minor-image-version,0 "CMakeFiles/lwip.dir/src/core/timers.c.obj" "CMakeFiles/lwip.dir/src/core/udp.c.obj" "CMakeFiles/lwip.dir/src/core/memp.c.obj" "CMakeFiles/lwip.dir/src/core/init.c.obj" "CMakeFiles/lwip.dir/src/core/pbuf.c.obj" "CMakeFiles/lwip.dir/src/core/tcp.c.obj" "CMakeFiles/lwip.dir/src/core/tcp_out.c.obj" "CMakeFiles/lwip.dir/src/core/sys.c.obj" "CMakeFiles/lwip.dir/src/core/netif.c.obj" "CMakeFiles/lwip.dir/src/core/def.c.obj" "CMakeFiles/lwip.dir/src/core/mem.c.obj" "CMakeFiles/lwip.dir/src/core/tcp_in.c.obj" "CMakeFiles/lwip.dir/src/core/stats.c.obj" "CMakeFiles/lwip.dir/src/core/inet_chksum.c.obj" "CMakeFiles/lwip.dir/src/core/ipv4/icmp.c.obj" "CMakeFiles/lwip.dir/src/core/ipv4/ip4.c.obj" "CMakeFiles/lwip.dir/src/core/ipv4/ip4_addr.c.obj" "CMakeFiles/lwip.dir/src/core/ipv4/ip_frag.c.obj" "CMakeFiles/lwip.dir/src/core/ipv6/ip6.c.obj" "CMakeFiles/lwip.dir/src/core/ipv6/nd6.c.obj" "CMakeFiles/lwip.dir/src/core/ipv6/icmp6.c.obj" "CMakeFiles/lwip.dir/src/core/ipv6/ip6_addr.c.obj" "CMakeFiles/lwip.dir/src/core/ipv6/ip6_frag.c.obj" "CMakeFiles/lwip.dir/custom/sys.c.obj"  -lkernel32 -luser32 -lgdi32 -lwinspool -lshell32 -lole32 -loleaut32 -luuid -lcomdlg32 -ladvapi32
CMakeFiles/lwip.dir/custom/sys.c.obj:sys.c:(.rdata$.refptr.btime_global[.refptr.btime_global]+0x0): undefined reference to `btime_global'
collect2.exe: error: ld returned 1 exit status
lwip/CMakeFiles/lwip.dir/build.make:659: recipe for target 'lwip/liblwip.dll' failed
```