changes in sbcl-0.8.7 relative to sbcl-0.8.6:

  * When built with the :SB-FUTEX feature, threaded builds now take
    advantage of the "fast userspace mutex" facility in Linux kernel 2.6
    for faster/more reliable mutex and condition variable support.
  * Incompatible change (but one you probably shouldn't have been using
    anyway): the interface and code for arbitrating between multiple
    threads in the same user session has been redesigned.
  * bug fix: GET-SETF-EXPANSION no longer throws an internal type
    error when called without an explicit environment argument.
    (thanks to Nikodemus Siivola)
  * bug fix: buffered :DIRECTION :IO streams are less likely to become
    confused about their position.  (thanks to Adam Warner and Gerd
    Moellmann)
  * bug fix: Pretty printing backquoted forms with unquotations in the
    argument list position of various code constructs such as LAMBDA
    now works correctly.  (reported by Paul Dietz)
  * bug fix: Pretty printing unquotations no longer loses all
    stream position information.
  * optimization: performance of string output streams is now less
    poor for multiple small sequence writes.
  * optimization: performance of CSUBTYPEP in the presence of complex
    expressions involving CONS and NOT many times has been improved.
    (reported by Paul Dietz)
  * ASDF-INSTALL bug fix: now parses *PROXY* properly.  (thanks to
    Sean Ross)
  * SB-SIMPLE-STREAMS enhancement: simple-streams can now be used as
    streams for the REPL, for the debugger, and so on.  (thanks to
    David Licteblau)
  * DEFINE-CODITION is more efficient.  (thanks to Brian Mastenbrook)
  * fixed some bugs revealed by Paul Dietz' test suite:
    ** the value of the :REHASH-THRESHOLD argument to MAKE-HASH-TABLE
       is ignored if it is too small, rather than propagating through
       to cause DIVIDE-BY-ZERO or FLOATING-POINT-OVERFLOW errors.
    ** extremely complex negations of CONS types were not being
       sufficiently canonicalized, leading to inconsistencies in
       SUBTYPEP.
    ** VALUES tranformer lost derived type.