pid_lock: Fix missing include under Linux & inconsistent whitespace

* And restore default config.mk for Linux
* Should have noticed before pushing...

Milestone: It works!

* Tested in real environment and it passes the authentication! The fields are correctly stitched together.
* The authentication server here does not check ANY field. Even if I remove `rjv3_append_common_fields` (only add the 62-byte header) it still passes the authentication.