Log Message:
Update to version 1.5.7

Changes between version 1.5.6 and version 1.5.7

  * platform support:
    many bug fixes to the experimental 64-bit PowerPC/Linux port, to the
    extent that the little-endian variant passes all applicable tests in
    the regression test suite; the big-endian variant currently has some
    failures
    experimental support for sb-threads on 64-bit PowerPC/Linux
    support threads on x86-64 Sun OS (#1841280)
    handle PAX restrictions on mprotect() on NetBSD
    experimental support for HaikuOS
    the runtime is built as a position-independent executable by default
    on x86-64 Linux and x86-64 Darwin
  * fixes and enhancements related to Unicode:
      update of the data files to Unicode 8.0
      fix a bug in the implementation of the Unicode line breaking algorithm
      regarding hebrew letters and hyphens
  * enhancement: add a restart to OPEN with :IF-EXISTS :ERROR to
    allow re-opening with :APPEND. (#806398, reported by Tobias
    Rittweiler)
  * bug fix: compiler optimizations on SEARCH with :FROM-END T
    didn't account for the empty sequence. (#1844821)
  * bug fix: handle SETF of nested empty VALUES correctly. (#1806478)
    optimization: FLOOR and CEILING on rationals are simpler, and
    the compiler's understanding of them is better.

Changes between version 1.5.5 and version 1.5.6

  * 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. (#1838442)
  * bug fix: compliant redefinition of classes whose previous definition
    caused argument mismatch errors does not generate errors any
    more. (#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. (#1838267)
    provide out-of-line definitions for internal machinery related to
    FLOAT-SIGN. (#1838337)
    include COMPLEX in the derived type of SIGNUM when appropriate. (#1838333)
    more correct internal type testing for function types. (#1838808,
    #1838888, #1838986)
    don't assume that all objects of type (NOT SIMPLE-ARRAY) have an array
    header. (#1838827)
    recognize that PHASE on non-positive numbers can return 0 as well as
    PI. (#1838892)