changes in sbcl-1.0.42 relative to sbcl-1.0.41

  * build changes
    ** Cross-compilation host is now specified to make.sh using
       command-line argument --xc-host=<command> instead of a positional
       argument. (thanks to Daniel Herring)
    ** Install location can be specified to make.sh using command-line
       argument --prefix=<path>. (lp#550889s, thanks to Daniel Herring)
  * optimization: The default implementation of
    COMPUTE-DISCRIMINATING-FUNCTION does much less wasted work.
  * enhancement: Explicit memory barrier operations are now available for use
    by multithreaded code.  See documentation for details.
  * enhancement: Experimental support for threading on Linux/PPC.
  * bug fix: RENAME-PACKAGE returns the package.  (Thanks to Eric Marsden)
  * bug fix: EXPT signals an error if first argument is a zero and second
    argument is a floating point zero. (lp#571581, thanks to Roman Marynchak)
  * bug fix: DEFTYPE signals an error for non-list lambda-lists.
    (lp#576594, thanks to Roman Marynchak)
  * bug fix: make ASDF-INSTALL compatible with the now-included ASDF2.
    (lp#612998, reported by Phil Hargett; patch from Jim Wise)