sbcl-1.5.6 released

Dear all,

I have released and uploaded sbcl-1.5.6 to all the usual places.  The
major change in this release is that the half-finished 64-bit PowerPC
port done by Brian Bokser last year has been three-quarter or
nine-tenths finished: I have seen reports that the system is able to run
SLIME on version 1 of the powerpc64 ABI, and that there is also support
for version 2 of the ABI.  Bug reports (and success reports) for this
and other features are welcome as always.  A summary of the changes in
this release is appended below.

Best wishes,

Christophe

changes in sbcl-1.5.6 relative to sbcl-1.5.5:
  * platform support:
    - experimental support for 64-bit PowerPC running Linux (extending Brian
      Bokser's work from 2018), on both the v1 and v2 ABIs
  * new feature: SB-EXT:SEARCH-ROOTS discovers paths from live objects to the
    roots keeping them alive.
  * enhancement: string output streams created with :ELEMENT-TYPE 'BASE-CHAR
    use internal buffers of BASE-STRING instead of UCS-4 strings restricted
    to the ASCII range, yielding a theoretical 4:1 space reduction.
  * optimization: improved make-array type derivation for multi-dimensional
    arrays. (lp#1838442)
  * bug fix: compliant redefinition of classes whose previous definition
    caused argument mismatch errors does not generate errors any more.
    (lp#1840595, reported by 3b on #sbcl)
  * bug fixes for issues caught by the random tester:
    - never derive the type of TRUNCATE on arbitrary numbers as the empty
      type.  (lp#1838267)
    - provide out-of-line definitions for internal machinery related to
      FLOAT-SIGN.  (lp#1838337)
    - include COMPLEX in the derived type of SIGNUM when appropriate.
      (lp#1838333)
    - more correct internal type testing for function types.  (lp#1838808,
      lp#1838888, lp#1838986)
    - don't assume that all objects of type (NOT SIMPLE-ARRAY) have an array
      header.  (lp#1838827)
    - recognize that PHASE on non-positive numbers can return 0 as well as PI.
      (lp#1838892)