The new macros, and indeed the previous macros, do not work on
Perl prior to 5.19.0 because the bug is actually how in Perl itself
handles the locale bits.  So we just go back to effectively always
saving the locale.  Resolves:

  https://rt.cpan.org/Ticket/Display.html?id=91987
$VERSION++ for CPAN release.
Isolate the locale testing to make it easier to deal with on Android.
On Android, strip out 'use locale' so that it doesn't fall over.
Correct spelling
Check USE_LOCALE
Better way to handle locale under Android
Final tweaks before releasing
That is lval not the length of the key
Stop supporting Perl releases prior to v5.6.2.  Tweak the code
to prevent locale from causing troubles where it cannot be used,
e.g. Android.
Move the locale stuff after the _un_vstring, so we don't accidentally strip the V-magic
Prevent bug in threads::shared from causing problems
Effective only for Perl < 5.19.8.