changes relative to sbcl-1.0.46:
* enhancement: --script muffles style-warnings and compiler notes. (lp#677779)
* enhancement: redefinition warnings for macros from different files. (lp#434657)
+ * enhancement: better MACHINE-VERSION on Darwin x86 and x86-64. (lp#668332)
* bug fix: SB-DEBUG:BACKTRACE-AS-LIST guards against potentially leaking
stack-allocated values out of their dynamic-extent. (lp#310175)
* bug fix: attempts to use SB-SPROF for wallclock profiling on threaded