add kill + example code

scheduler.kill seems like its not implemented comletly or doest work as
expected.

kernel/syscall/handler.cc

@@ -66,6 +66,9 @@ extern "C" size_t syscall_handler(size_t sysnum, size_t p1, size_t p2,
          case Syscall::ID::SYS_EXIT:
             Syscall::Skeleton::exit(Guard::enter().vault());
             return 0;
+         case Syscall::ID::SYS_KILL:
+            Syscall::Skeleton::kill(Guard::enter().vault(),p1);
+            return 0;
      }
 
 	return static_cast<size_t>(-1);