UPDATE: Patches for t/run/locale.t and ext/POSIX/t/posix.t have been submitted to perlbug - see https://rt.perl.org/Ticket/Display.html?id=133417
UPDATE 2: Those patches to t/run/locale.t and ext/POSIX/t/posix.t have now been applied to bleadperl.

Oh ... I failed to specifically thank you for providing those 2 patches.
I'll certainly be including them as I think that -Ud_strtod builds should be supported.
With current perl source there's no point in building with -Ud_strtod (or -Ud_strtold) but with the patches I'm proposing, those switches provide the simplest way to resort to using perl's Atof for assigning floating point values.
I don't expect that anyone in their right mind would want to opt for using perl's Atof, but I think the option should remain and the test suite should pass all tests.

Cheers,
Rob