[perl #66104] Bugs in extended regexp features

[perl #66104] Bugs in extended regexp features

More precisely: Make run-time (?{...}) inherit pragmata.

This commit makes Perl_sv_compile_2op_is_broken (nice name!) copy the
hints from PL_curcop if invoked during run time. Usually they are
inherited from the code that is currently being compiled (which works
for $foo =~ /(?{...})/), but the code currently being compiled is not
the enclosing scope at run time ($bar = '(?{...})'; $foo =~ $bar),
hence the need for copying in a similar manner to pp_entereval.

Theoretically this code should also have to avoid copying a statement
label, but goto inside a regexp eval does not currently work, so I
cannot prove or disprove that yet.