Kernel: Add new syscall to allow changing the system date

Author: https://github.com/supercomputer7
Commit: 4484513b45
Pull-request: https://github.com/SerenityOS/serenity/pull/1396
Reviewed-by: https://github.com/awesomekling
Reviewed-by: https://github.com/shannonbooth ✅

Kernel/Process.h

@@ -213,6 +213,7 @@ public:
     int sys$usleep(useconds_t usec);
     int sys$gettimeofday(timeval*);
     int sys$clock_gettime(clockid_t, timespec*);
+    int sys$clock_settime(clockid_t, timespec*);
     int sys$clock_nanosleep(const Syscall::SC_clock_nanosleep_params*);
     int sys$gethostname(char*, ssize_t);
     int sys$uname(utsname*);