Apparently a bad reversion while resolving some repo conflicts.

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

Exported *supports-threads-p* so that apps can check that variable.
Some other small changes to make it load and 'work' on clisp.

* 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.