Added thread group identification to c0 and libl4

tgid will be used when threads will be created in same address space.

src/api/syscall.c

@@ -71,6 +71,8 @@ int sys_getid(syscall_context_t *regs)
 
 	ids->tid = this->tid;
 	ids->spid = this->spid;
+	ids->tgid = this->tgid;
+
 	return 0;
 }
 

src/api/thread.c

@@ -175,6 +175,12 @@ out:
 		if ((ids->spid = id_get(space_id_pool,
 					ids->spid)) < 0)
 			ids->spid = id_new(space_id_pool);
+
+		/* It also gets a thread group id */
+		if ((ids->tgid = id_get(tgroup_id_pool,
+					ids->tgid)) < 0)
+			ids->tgid = id_new(tgroup_id_pool);
+
 	}
 
 	/* Set all ids */