delete PERL_YAML_BACKEND and PERL_JSON_BACKEND in T/TEST

If these are set, Parse-CPAN-Meta and other things that depend
on it may fail.
Add --libpods back as a non-functional option to pod2html.

When --libpods was removed, this broke backward compatiblility with
existing uses.  This change adds back the option, but warns that
--libpods is no longer supported.
Disable optimizer for 32bit PA-RISC builds on HP-UX

The (ANSI) C compiler fails to compile precompiled (.i) files when both
-g and -O (all +O1 and above) are given. When -g is requested, -O, +O,
and +Onolimit are removed from optimize flags

This #fail does not occur with the newer aCC compiler B3910B, which is
also used on HP-UX on Itanium.

The check/modification has to be done as late as possible, as the other
options, like -Duse64bitall and -DDEBUGING, will modify the variables
that need to be checked after hints/hpux.sh has been dealt with.
check for PA* in both branches of case

(thanks ilmari for spotting)
with 5.16.0, 5.12.x is security-only
Increase $PerlIO::scalar::VERSION to 0.14
[perl #112780] Don’t set cloned in-memory handles to ""

PerlIO::scalar’s dup function (PerlIOScalar_dup) calls the base imple-
mentation (PerlIOBase_dup), which pushes the scalar layer on to the
new file handle.

When the scalar layer is pushed, if the mode is ">" then
PerlIOScalar_pushed sets the scalar to the empty string.  If it is
already a string, it does this simply by setting SvCUR to 0, without
touching the string buffer.

The upshot of this is that newly-cloned in-memory handles turn into
the empty string, as in this example:

use threads;
my $str = '';
open my $fh, ">", \$str;
$str = 'a';
async {
    warn $str;  # something's wrong
}->join;

This has probably always been this way.

The test suite for MSCHWERN/Test-Simple-1.005000_005.tar.gz does some-
thing similar to this:

use threads;
my $str = '';
open my $fh, ">", \$str;
print $fh "a";
async {
    print $fh "b";
    warn $str;  # "ab" expected, but 5.15.7-9 gives "\0b"
}->join;

What was happening before commit b6597275 was that two bugs were can-
celling each other out: $str would be "" when the new thread started,
but with a string buffer containing "a" beyond the end of the string
and $fh remembering 1 as its position.  The bug fixed by b6597275 was
that writing past the end of a string through a filehandle was leaving
junk (whatever was in memory already) in the intervening space between
the old end of string and the beginning of what was being written to
the string.  This allowed "" to turn magically into "ab" when "b" was
written one character past the end of the string.  Commit b6597275
started zeroing out the intervening space in that case, causing the
cloning bug to rear its head.

This commit solves the problem by hiding the scalar temporarily
in PerlIOScalar_dup so that PerlIOScalar_pushed won’t be able to
modify it.

Should PerlIOScalar_pushed stop clobbering the string and should
PerlIOScalar_open do it instead?  Perhaps.  But that would be a bigger
change, and we are supposed to be in code freeze right now.
Fix test failure

Lesson learnt: After switching from threaded to unthreaded and fixing
the test, switch back again and re-run the test. :-)
whichsig nul-cleanup.

This adds _pv, _pvn, and _pv versions of whichsig() in mg.c, which
get both kill "NAME" and %SIG lookup nul-clean.
perldelta: Explain stdio/sfio future deprecation.
perl5160delta: tweaks

sdio -> stdio
two spaces after dots
Skip Carp tests on VMS.

They want IPC::Open3::open3, which is not currently working.
[rt.cpan.org #61577] sockdomain and socktype undef on newly accepted sockets

There appears to be a flaw in IO::Socket where some IO::Socket objects
are unable to properly report their socktype, sockdomain, or protocol
(they return undef, even when the underlying socket is sufficiently
initialized to have these properties).

The attached patch should cover IO::Socket objects created via accept(),
new_from_fd(), new(), and anywhere else whose details haven't been
properly cached.

No new code should be executed on IO::Socket objects whose details are
already cached and present.
sometimes fork() isn't available

This was amended from the original Tony prepared in a parallel branch
add Test::More as a prereq to Makefile.PL
bump version to 5.16.0 RC0

Done with:

  ./perl -Ilib Porting/bump-perl-version -i 5.15.9 5.16.0

...followed by a small edit to INSTALL and patchlevel.h.
remove perl515*delta, add perl5160delta
regenerate uconfig.h
update .gitignore: we generate 5160delta now
okay the links to CPAN modules in the perldelta