utf8: add tests for behavior change in v5.15.6-407-gc710240, and more

In v5.15.6-407-gc710240 Father Chrysostomos patched utf8::decode() so it
would call SvPV_force_nolen() on its argument. This meant that calling
utf8::decode() with a non-blessed non-overloaded reference would now
coerce the reference scalar to a string, i.e. before we'd do:

    $ ./perl -Ilib -MDevel::Peek -wle 'use strict; print $]; my $s = shift; my $s_ref = \$s; utf8::decode($s_ref); Dump $s_ref; print $$s_ref' ævar
    5.019011
    SV = IV(0x2579fd8) at 0x2579fe8
      REFCNT = 1
      FLAGS = (PADMY,ROK)
      RV = 0x25c33d8
      SV = PV(0x257ab08) at 0x25c33d8
        REFCNT = 2
        FLAGS = (PADMY,POK,pPOK)
        PV = 0x25a1338 "\303\246var"\0
        CUR = 5
        LEN = 16
    ævar

But after calling SvPV_force_nolen(sv) we'd instead do:

    $ ./perl -Ilib -MDevel::Peek -wle 'use strict; print $]; my $s = shift; my $s_ref = \$s; utf8::decode($s_ref); Dump $s_ref; print $$s_ref' ævar
    5.019011
    SV = PVIV(0x140e4b8) at 0x13e7fe8
      REFCNT = 1
      FLAGS = (PADMY,POK,pPOK)
      IV = 0
      PV = 0x140c578 "SCALAR(0x14313d8)"\0
      CUR = 17
      LEN = 24
    Can't use string ("SCALAR(0x14313d8)") as a SCALAR ref while "strict refs" in use at -e line 1.

I think this is arguably the right thing to do, we wouln't actually utf8
decode the containing scalar so this reveals bugs in code that passed
references to utf8::decode(), what you want is to do this instead:

    $ ./perl -CO -Ilib -MDevel::Peek -wle 'use strict; print $]; my $s = shift; my $s_ref = \$s; utf8::decode($$s_ref); Dump $s_ref; print $$s_ref' ævar
    5.019011
    SV = IV(0x1aa8fd8) at 0x1aa8fe8
      REFCNT = 1
      FLAGS = (PADMY,ROK)
      RV = 0x1af23d8
      SV = PV(0x1aa9b08) at 0x1af23d8
        REFCNT = 2
        FLAGS = (PADMY,POK,pPOK,UTF8)
        PV = 0x1ad0338 "\303\246var"\0 [UTF8 "\x{e6}var"]
        CUR = 5
        LEN = 16
    ævar

However I think we should be more consistent here, e.g. we'll die when
utf8::upgrade() gets passed a reference, but utf8::downgrade() just
passes it through. I'll file a bug for that separately.
Add pod/perl5182delta.pod
RMG - Update note about adding new perldelta in BLEAD-FINAL/MAINT releases
perl5182delta typo fixes

Escaping fix.

Missing full stop added.
fix documentation of HeUTF8 return value
Correct typo in commit b38d7779bd
File-Glob/t/basic.t: avoid race condition

Test 2 does a glob('*') in the t/ directory, and compares that with the
results of readdir('.'). If we're doing parallel testing, temporary files
and stuff may get created in t/, resulting in a race condition and
occasional random failures.

Fix this by chdir()ing to t/base/ first. The timestamp on this directory
on my system seems to indicate that nothing currently creates tmp files in
that dir, and given that these are basic tests, that's relatively unlikely
to change.
Porting/acknowledgements.pl - Use correct quotes in perl command-line
Synchronise Carp with CPAN version 1.3301
properly reset ReadLine's knowledge of handles after pager

[perl #121456]
add Hiroo Hayashi to AUTHORS
bump version on debugger
RT-121512 - Allow -I/dir/ with trailing slash to find .pmc files.

6b0bdd7f2041803dc3ec72b53d28052705861967 updated -I to not add a
trailing '/' if one was already present, but failed to update the
length of the resulting SV to account for the lack of another character.
This caused later checks based off of that length to fail (in this case,
seeing if the last 3 characters of the string are .pm).
Missed perldelta for 437e3a7 (for v5.19.8)
nitpicks
speed up miniperl require on Win32

These 3 optimizations reduce the number of, usually failing, I/O calls
for each "require" for miniperl only. None are appropriate except for
Win32. See #121119 for details.
tighten Storable's recognition of tied SVs

Since commit ff44333e5a9d9dca5272bb166df463607ebd3020, being RMAGICAL
and having tie magic is not sufficient to recognise an SV as tied.
When magic is turned off for mg_set(), the RMAGICAL flag is now left on,
so that vstrings will be recognised as such.  So Storable needs to check
whether the tie magic it sees is actually in effect, by also looking at
the GMAGICAL and SMAGICAL flags.