reparse compile-time /(?{})/ in right scope

When a compile-time regex like /...(?{ code-block }) .../
is compiled in the presence of constant and concat overloading,
this can cause (still at compile-time) for the pattern to be evaled and
re-compiled, in order to re-compile any code-blocks that got messed up
during the overloading and thus whose text no longer matches that which
the perl parser previously compiled.

When this happens, eval_sv() happens to be called when the perl parser is
still in compiling state; normally its called from running state.
This tickles an undiscovered bug in Perl_find_runcv_where(), which
finds the current cop sequence by looking at PL_curcop->cop_seq.
At compile time, we need to get it from PL_cop_seqmax instead.

(cherry picked from commit c3923c33af542d8764d5a1e4eb5d7b311f443b89)
[perl #114864] Make UNIVERSAL::DESTROY changes invalidate caches

Commit 8c34e50d inadvertently caused DESTROY caches not to be
reset when UNIVERSAL::DESTROY changes.  Normally, a change to
a method will cause mro_method_changed_in to be called on all
subclasses, but mro.c cheats for UNIVERSAL and just does
++PL_sub_generation.  So clearing the DESTROY cache explicitly
in mro_method_changed_in is clearly not enough.

(cherry picked from commit c716b3beb77406159d18fd52251821fee641f9fc)
File::Glob: Dup glob state in CLONE()

This solves [perl #119897] and [perl #117823], and restores the
behavior of glob() in conjunction with threads of 5.14 and older.

Since 5.16, code that used glob() inside a thread had been
unintentionally sharing state between threads, which lead to things
like this crashing and failing assertions:

./perl -Ilib -Mthreads -e 'scalar glob("*"); threads->create(sub { glob("*") })->join();'

(cherry picked from commit facf34ef484d62d15b2da11ee03d01942a22ff15)
Fix ext/File-Glob/t/threads.t filenames for VMS.

As noted in

http://www.nntp.perl.org/group/perl.perl5.porters/2013/09/msg208134.html

zero-length extensions always get a trailing dot on VMS, and the
easiest workaround is to always use an explicit extension.

(cherry picked from commit 43ed1b742e2b7be9184e1fb35c0f68d15b87feed)
bump File::Glob version for 5.18.2
update perldelta for File::Glob version bump