perlapi: Document some macros
File::Glob: Drop dependency on given/when
Porting/checkpodencoding.pl: Drop dependency on smartmatch
Porting/core-cpan-diff: Drop dependency on smartmatch
t/re/regexp_unicode_prop.t: Drop dependency on given/when
t/porting/dual-life.t: Drop dependency on smartmatch
Make smartmatch, given & when experimental
perldelta for the new warnings
Silence "smartmatch is experimental" warnings in autodie
Improve how regcomp.pl handles multibits

In preparation for future changes.
simplify regcomp.c by using vars to avoid repeated macros

Use two temporary variables to simplify the logic, and maybe
speed up a nanosecond or two.

Also chainsaw some long dead logic. (I #ifdef'ed it out years ago)
rework split() special case interaction with regex engine

This patch resolves several issues at once. The parts are
sufficiently interconnected that it is hard to break it down
into smaller commits. The tickets open for these issues are:

  RT #94490  - split and constant folding
  RT #116086 - split "\x20" doesn't work as documented

It additionally corrects some issues with cached regexes that
were exposed by the split changes (and applied to them).

It effectively reverts 5255171e6cd0accee6f76ea2980e32b3b5b8e171
and cccd1425414e6518c1fc8b7bcaccfb119320c513.

Prior to this patch the special RXf_SKIPWHITE behavior of

    split(" ", $thing)

was only available if Perl could resolve the first argument to
split at compile time, meaning under various arcane situations.

This manifested as oddities like

    my $delim = $cond ? " " : qr/\s+/;
    split $delim, $string;

and

    split $cond ? " ", qr/\s+/, $string

not behaving the same as:

    ($cond ? split(" ", $string) : split(/\s+/, $string))

which isn't very convenient.

This patch changes this by adding a new flag to the op_pmflags,
PMf_SPLIT which enables pp_regcomp() to know whether it was called
as part of split, which allows the RXf_SPLIT to be passed into run
time regex compilation. We also preserve the original flags so
pattern caching works properly, by adding a new property to the
regexp structure, "compflags", and related macros for accessing it.
We preserve the original flags passed into the compilation process,
so we can compare when we are trying to decide if we need to
recompile.

Note that this essentially the opposite fix from the one applied
originally to fix #94490 in 5255171e6cd0accee6f76ea2980e32b3b5b8e171.
The reverted patch was meant to make:

        split( 0 || " ", $thing )            #1

consistent with

        my $x=0; split( $x || " ", $thing )  #2

and not with

        split( " ", $thing )                 #3

This was reverted because it broke C<split("\x{20}", $thing)>, and
because one might argue that is not that #1 does the wrong thing,
but rather that the behavior of #2 that is wrong. In other words
we might expect that all three should behave the same as #3, and
that instead of "fixing" the behavior of #1 to be like #2, we should
really fix the behavior of #2 to behave like #3. (Which is what we did.)

Also, it doesn't make sense to move the special case detection logic
further from the regex engine. We really want the regex engine to decide
this stuff itself, otherwise split " ", ... wouldn't work properly with
an alternate engine. (Imagine we add a special regexp meta pattern that behaves
the same as " " does in a split /.../. For instance we might make
split /(*SPLITWHITE)/ trigger the same behavior as split " ".

The other major change as result of this patch is it effectively
reverts commit cccd1425414e6518c1fc8b7bcaccfb119320c513, which
was intended to get rid of RXf_SPLIT and RXf_SKIPWHITE, which
and free up bits in the regex flags structure.

But we dont want to get rid of these vars, and it turns out that
RXf_SEEN_LOOKBEHIND is used only in the same situation as the new
RXf_MODIFIES_VARS. So I have renamed RXf_SEEN_LOOKBEHIND to
RXf_NO_INPLACE_SUBST, and then instead of using two vars we use
only the one. Which in turn allows RXf_SPLIT and RXf_SKIPWHITE to
have their bits back.
fix comment, reindent and add parenthesis for clarity

I had to stare at this expression and make sure there wasn't
anything tricky for too long, so I added parens, and reindented
it.
prevent SEGV from buffer read overrun, and refactor away duplicated code

The split patch introduced a buffer read overrun error in sv_dump() when
stringifying empty strings. This bug was always existant but was probably
never triggered because we almost always have at least one extflags set,
so it never got an empty buffer to show. Not so with the new compflags. :-(
eliminate the only internal uses of HvFILL

The usages are as far as I know incorrect anyway. We resize
the hash bucket array based on the number of keys it holds,
not based on the number of buckets that are used, so this
usage was wrong anyway.

Another bug that this revealed is that the old code would allow
HvMAX(hv) to fall to 0, even though every other part of the
core expects it to have a minimum of 7 (meaning 8 buckets).

As part of this we change the hard coded 7 to a defined constant
PERL_HASH_DEFAULT_HvMAX.

After this patch there remains one use of HvFILL in core, that used
for scalar(%hash) which I plan to remove in a later patch.
Exporter on CPAN is 5.68 make blead reflect this
makedef.pl shouldn't prepend Perl_ to symbols already starting with Perl_.

In the next patch, I have Perl_croak_memory_wrap defined in embed.fnc with
the 'nroX' flags, since this is a private function used by public macros.
I used the long form of the name Perl_croak_memory_wrap everywhere, and
used the 'o' flag so that embed.h wouldn't contain a useless #define
croak_memory_wrap Perl_croak_memory_wrap.  Unfortunately, makedef.pl
(used by the Win32 build process) didn't know what to do with that entry
and created an entry Perl_Perl_croak_memory_wrap.   Changing makedef.pl
to use the 'o' flag to decide whether to add the Perl_ prefix resulted
in over 50 other symbols changing in the output of makedef.pl.  I don't
know if the changes are correct or if the 'o' flag is in error on those
entries in embed.fnc, but I don't have time to check them all out.

This patch just stops makedef.pl from adding a Perl_ prefix if there is
already one there.
Remove the non-inline function S_croak_memory_wrap from inline.h.

This appears to resolve these three related tickets:

    [perl #116989] S_croak_memory_wrap breaks gcc warning flags detection
    [perl #117319] Can't include perl.h without linking to libperl
    [perl #117331] Time::HiRes::clock_gettime not implemented on Linux (regression?)

This patch changes S_croak_memory_wrap from a static (but not inline)
function into an ordinary exported function Perl_croak_memory_wrap.
This has the advantage of allowing programs (particuarly probes, such
as in cflags.SH and Time::HiRes) to include perl.h without linking
against libperl.  Since it is not a static function defined within each
compilation unit, the optimizer can no longer remove it when it's not
needed or inline it as needed.  This likely negates some of the savings
that motivated the original commit 380f764c1ead36fe3602184804292711.
However, calling the simpler function Perl_croak_memory_wrap() still
does take less set-up than the previous version, so it may still be a
slight win.  Specific cross-platform measurements are welcome.
Fix perlfunc.pod to reflect changes to split " " logic
improve hash related documentation in perlfunc and perlsec to reflect new hash randomization logic