Thanks to Kilian Sprotte for reporting this.

  * Remove BT-SYSTEM package while preserving LOADability
    of .asd files.

  * Move test suite related bits from BT's TEST-OP to new
    BT-TEST's TEST-OP.

  * Make BT's TEST-OP simply invoke BT-TEST's TEST-OP.

Finished conversion from methods to functions with defaults (Stelian Ionescu <sionescu@common-lisp.net>)

Centralized loading and checking of impl-specific thread libraries (Stelian Ionescu <sionescu@common-lisp.net>)

Added a file containing the MIT license and a copyright and license notice in
each source file

* ABCL's version of ASDF doesn't support :serial;
* EXT:MAKE-THREAD-LOCK appears to be a thunk; and
* EXT:THREAD-LOCK doesn't return T on success.