[kservice] Update show version year info to 2018.

src/kservice.c

@@ -542,7 +542,7 @@ void rt_show_version(void)
     rt_kprintf("- RT -     Thread Operating System\n");
     rt_kprintf(" / | \\     %d.%d.%d build %s\n",
                RT_VERSION, RT_SUBVERSION, RT_REVISION, __DATE__);
-    rt_kprintf(" 2006 - 2017 Copyright by rt-thread team\n");
+    rt_kprintf(" 2006 - 2018 Copyright by rt-thread team\n");
 }
 RTM_EXPORT(rt_show_version);