changes in sbcl-1.0.50 relative to sbcl-1.0.49:

  * enhancement: errors from FD handlers now provide a restart to remove
    the offending handler.
  * enhancement: SB-INTROSPECT:FIND-DEFINITION-SOURCE now works on structure
    copiers as well.
  * enhancement: location of user or system initialization file can now easily
    be customized for saved cores. See: SB-EXT:*USERINIT-PATHNAME-FUNCTION*
    and SB-EXT:*SYSINIT-PATHNAME-FUNCTION*.
  * enhancement: SB-EXT:MAKE-THREAD accepts an argument list designator for
    the thunk, as a keyword argument, :arguments.
  * enhancement: constraint propagation is simplified (and sped up) when
    COMPILATION-SPEED > SPEED.
  * enhancement: SB-ALIEN exports alien type specifiers SIZE-T and OFF-T.
  * enhancement: debugger understands &MORE arguments better.
  * optimization: extracting bits of a single-float on x86-64 has been
    optimized. (lp#555201)
  * optimization: MAP and MAP-INTO are more efficient for non-simple vectors,
    when (> SPEED SPACE).
  * optimization: local call trampolines (x86 and x86-64) are emitted
    inline.
  * optimization: implicit value cells for dynamic-extent closed-over bindings
    on x86 and x86-64 can hold unboxed values as well.
  * meta-optimization: improved compilation speed, especially for large
    functions. (lp#792363 and lp#394206)
  * bug fix: bound derivation for floating point operations is now more
    careful about rounding possibly closing open bounds. (lp#793771)
  * bug fix: SB-POSIX:SYSCALL-ERROR's argument is now optional. (accidental
    backwards incompatible change in 1.0.48.27)
  * bug fix: occasional debugger errors in when a type-error occured in a
    function with dynamic-extent &rest list.
  * bug fix: &optional and &key supplied-p arguments in DEFSTRUCT
    boa-construtors can be used to initialized structure slots.
  * bug fix: FMAKUNBOUND removes the MACRO-FUNCTION, should one exist.
    (lp#795705, regression)
  * bug fix: DIRECTORY works better on logical pathnames.
  * bug fix: RUN-PROGRAM no longer fails spuriously when argument strings
    are of the order of ARRAY-TOTAL-SIZE-LIMIT. (lp#787237)
  * bug fix: the compiler no longer constant-folds NaNs in
    MAKE-{SINGLE,DOUBLE}-FLOAT. (lp#486812)
  * bug fix: FORMAT now handles floating point rounding correct, eg.
    (format nil "~,1F" 0.01) => "0.0" instead of "0.01" as previously.
    (lp#308961)
  * bug fix: style warning during lambda-list introspection of generic
    functions with both optional and key argments.
  * bug fix: regalloc doesn't barf on unused TNs due to type-directed constant
    folding. (lp#729765)
  * bug fix: Fixed an off-by-one in MAP-ALLOCATED-OBJECTS that might have caused
    infinite loops.