[perl #70151] eval localises %^H at runtime

[perl #70151] eval localises %^H at runtime

It doesn’t any more.

Now the hints are localised in a separate inner scope surrounding the
call to yyparse.  This meant moving hint-handling code from pp_require
and pp_entereval into S_doeval.

Some tests in t/comp/hints.t were testing for the buggy behaviour, so
they have been adjusted.

Basically, this fixes

    sub import {
        eval "strict->import"
    }

which should work the same way as

    sub import {
        strict->import
    }

but was not working because %^H and $^H were being localised to
the eval at its run time, not just its compilation.  So the values
assigned to %^H and $^H at the eval’s run time would simply be lost.