0.9.18.62:

    FreeBSD threads fixes, based on the patches from NIIMI Satoshi
    on the sbcl-devel mailing list. This makes FreeBSD threads "work",
    finally, at least experimentally.

    * added lutex_trylock routine.
    * fix the sb-lutex and (not wait-p) case of get-lutex.
    * add pthred_mutexattr_t field to the lutex lisp object.
    * use libthr (1:1 threading) instead of libpthread (m:n threading)
      which supposedly doesn't work.
    * use PTHREAD_MUTEX_ERRORCHECK when attribute locking mutexes
    * create a dedicated cleanup thread to free threads
    * put a mutex around creating threads
    * use load_fs instead of the inline asm stubs