changes in sbcl-1.0.53 relative to sbcl-1.0.52:
  * enhancement: on 64-bit targets, in src/compiler/generic/early-vm.lisp,
    the parameter n-fixnum-tag-bits may now vary from 1 (fixnum =
    (signed-byte 63)) to 3 (fixnum = (signed-byte 61)) at build-time.
  * enhancement: SB-EXT:WAIT-FOR allows waiting for arbitrary events.
  * minor(?) incompatible(?) change: The default fixnum width on 64-bit
    targets is now 63 bits (up from 61).
  * enhancement: DESCRIBE now reports a lambda-list and source location
    for complext setf-expanders.
    GETF, LOGBITP, LDB, and MASK-FIELD now arrange for non-primary values
    of multiple-valued places to be set to NIL, instead of signalling an
    error (per a careful reading of CLHS
  * bug fix: floating-point traps now work on darwin/x86 and /x86-64.
  * bug fix: repair crash in x86oid darwin signal handling emulation
    when built with certain compilers.
  * bug fix: SB-ROTATE-BYTE misrotated to the right when using constant
    rotation arguments on x86-64. (lp#882151)
  * bug fix: low-level control flow optimisations could result in bogus
    code in functions with tail and non-tail calls to local functions on
    x86oids. (lp#883500)
  * bug fix: on SPARC/:sb-unicode, avoid crashing the assembler by trying
    to emit literal characters > (code-char 4095), for comparisons with
    constant characters.
  * bug fix: ROOM reported only the low 32 bits of dynamic space usage
    on 64 bit platforms. (lp#881445)
  * bug fix: DELETE-FILE did not MERGE-PATHNAMES, making it possible to
    delete the wrong file when using relative pathnames. (lp#882877)
  * bug fix: optimized SEARCH of vectors-on-vectors mishandled zero-length
    sequences and :KEY NIL.

Juho Snellman