make: recipe for target 'sloxy' failed on Ubuntu 18.04

```
> make sloxy
cc sloxy.c -o sloxy
sloxy.c:1:2: warning: #import is a deprecated GCC extension [-Wdeprecated]
#import
^~~~~~
sloxy.c:2:2: warning: #import is a deprecated GCC extension [-Wdeprecated]
#import
^~~~~~
sloxy.c:3:2: warning: #import is a deprecated GCC extension [-Wdeprecated]
#import
^~~~~~
sloxy.c:4:2: warning: #import is a deprecated GCC extension [-Wdeprecated]
#import
^~~~~~
sloxy.c:5:2: warning: #import is a deprecated GCC extension [-Wdeprecated]
#import
^~~~~~
sloxy.c:6:2: warning: #import is a deprecated GCC extension [-Wdeprecated]
#import
^~~~~~
sloxy.c:7:2: warning: #import is a deprecated GCC extension [-Wdeprecated]
#import
^~~~~~
sloxy.c:8:2: warning: #import is a deprecated GCC extension [-Wdeprecated]
#import
^~~~~~
sloxy.c:9:2: warning: #import is a deprecated GCC extension [-Wdeprecated]
#import
^~~~~~
sloxy.c:10:2: warning: #import is a deprecated GCC extension [-Wdeprecated]
#import
^~~~~~
sloxy.c:11:2: warning: #import is a deprecated GCC extension [-Wdeprecated]
#import
^~~~~~
sloxy.c:12:2: warning: #import is a deprecated GCC extension [-Wdeprecated]
#import
^~~~~~
sloxy.c:13:2: warning: #import is a deprecated GCC extension [-Wdeprecated]
#import
^~~~~~
sloxy.c: In function ‘main’:
sloxy.c:62:19: error: ‘struct sockaddr_in’ has no member named ‘sin_len’; did you mean ‘sin_zero’?
listen_sockaddr->sin_len = sizeof *listen_sockaddr;
^~~~~~~
sin_zero
sloxy.c:133:21: error: ‘struct sockaddr_in’ has no member named ‘sin_len’; did you mean ‘sin_zero’?
target_sockaddr->sin_len = sizeof *target_sockaddr;
^~~~~~~
sin_zero
sloxy.c: In function ‘readwrite’:
sloxy.c:198:2: warning: implicit declaration of function ‘nanosleep’; did you mean ‘usleep’? [-Wimplicit-function-declaration]
nanosleep(&tv, NULL);
^~~~~~~~~
usleep
: recipe for target 'sloxy' failed
make: *** [sloxy] Error 1
```

Start by running `make sloxy` on Ubuntu 18.04 and inspect the reported lines in `sloxy.c`, especially the `sockaddr_in` setup and `nanosleep` call. Check the relevant system declarations and confirm that the proxy still builds successfully with the warnings and errors addressed.

Written by the indexing model from the issue text.