Remove an OpenBSD note in the README which is no longer necessary.

OpenBSD's behavior has not changed, but the default SBCL allocation
size was changed some time ago to work with the default OpenBSD
resource limits.
Clean up OpenBSD makefile fragments a little.

It seems -export-dynamic is no longer necessary for
tools-for-build. Perhaps it never was, and I was just confused.
ensure-directories-exist: Signal an error when trying to create a
directory with the same name as an existing file.

Previously (ensure-directories-exist "/foo/bar/"), where /foo/bar is a
regular file, just silently returned "/foo/bar/", NIL.
Make SBCL buildable by Clang.

The only changes needed were a modification to use $CC when building
contribs, and inline declaration incompatibility for a couple of
functions.

Closes lp#658414.
Closes https://bugs.launchpad.net/sbcl/+bug/911027

Fix copy-structure.  When copying from stack to heap, garbage could
end up in the heap making GC unhappy.  Thanks to James Knight.
Don't signal a note on NOTINLINE non-toplevel functions.

When a function was declared NOTINLINE, and later defined not at the
toplevel, SBCL signaled a note saying that it can't inline it.

Fixes lp#963530.
Fixup fewer complaints about hairy lexical environments

In particular, if the function has been requested NOTINLINE, and that name
has never been INLINE or MAYBE-INLINE, there should be no compiler note.
Include a test case and a NEWS entry for posterity.
Fix build on PPC/Darwin
contrib/asdf: Import asdf 2.20 from upstream.

   * lp#933112
clarify the make.sh --with-feature and --without-feature syntax in INSTALL

  Documentation-only, so going in despite the freeze.
Add an entry for ASDF upgrade to NEWS
Add workaround to a flaky semaphore timeout test.
1.0.56: will be tagged as "sbcl-1.0.56"
better REPLACE docstring

  lp#965592
sb-simple-streams: signal an error for bad stream classes in OPEN

  Instead of silently returning NIL, signal an error if the class does not
  exist (if argument :class is a symbol) or is not a stream class.

  lp#969352
don't refer to unix namestrings on windows
plain T and OTHERWISE not allowed in CASE normal-clauses

  lp#959687
more conservative classoid-name clearing

  (SETF (FIND-CLASS X) NIL) should not clear the classoid name if X is
  not the proper name of the class.

  lp#941102
MAKE-LEXENV used NCONC on its arguments, which callers did not expect

  Fixes lp#924276.
gencgc: reclaim space more aggressively

 * When considering auto_gc_trigger, take the number of bytes about to be
   allocated into account.

 * If bytes_consed_between_gcs is more than the amount of free heap, set next
   GC to occur when half of the remaining free heap has been consumed.

 * Keep track of the size of the largest object allocated between two GCs.
   When collecting garbage, if there isn't enough space to allocate at least
   two such objects before collecting the last generation due a collection,
   extend the collection by one extra generation.

   This works around our tendency to immediately promote large objects to
   generation 1, due to auto_gc_trigger causing a GC _after_ the allocation.

 Fixes lp#936304.