sbcl-2.2.3 released

Dear all,

I have just built and tagged sbcl; various artifacts are already
available at SourceForge, and I expect more will come along in the next
few days.  The main changes in this release are listed below.

Best wishes,

Christophe

changes in sbcl-2.2.3 relative to sbcl-2.2.2:
  * minor incompatible change: SB-THREAD:MUTEX-OWNER may return :THREAD-DEAD
    if the apparent owner either exited nearly instantly after releasing the
    mutex (and is not now the owner), or died and never released it.
  * minor incompatible change: building the system with the simple semi-space
    copying collector is no longer supported.
  * minor incompatible change: support for PPC/Darwin has been removed.
  * platform support:
    ** fix regressions in threads on RISC-V.  (lp#1962598)
    ** threads are now enabled by default on RISC-V.
    ** The generational garbage collector is now supported on MIPS.
  * optimization: fasls containing standard object literals are now smaller
    and load more efficiently.
  * optimization: faster arithmetic (*-+) on word-sized integers when the
    result is not known to fit into a word (ARM64 and x86-64).
  * bug fix: EQness of constants is now always preserved when block compiling.