changes in sbcl-1.4.15 relative to sbcl-1.4.14:
* enhancement: added AVX2 instructions on x86-64, which can be used with
SB-SIMD-PACK.
* enhancement: specializer name parsing is less lenient and signals a
specific condition in case of syntax errors. (lp#1808681)
* enhancement: provide interactive restarts for some file-system errors.
* enhancement: COMPILE no longer acquires the world lock.
(fixes most occurrences of lp#308959)
* bug fix: RUN-PROGRAM is more responsive and less likely to deadlock
(lp#1702178, lp#1808641)
* bug fix: traceroot can search for simple-fun targets (lp#1808659, reported
by Michal Herda)
* compiler bug fixes:
** related to code generation: lp#1805899, lp#1806982, lp#1807455
** related to interpreting and constant-folding: lp#1806513
** related to the type system: lp#1804759, lp#1804796
** related to eq-testing of structure slots: lp#1809582, lp#1808273
** related to dynamic-extent: lp#1809565, lp#1809253, lp#1809485,
lp#1739652
** related to GC safety: lp#308949