New warnings in blead (was RFC: deprecate calling isFOO_utf8() withmalformed UTF-8)

Since commit 281235491e0eef7be051126b2c99109c4f5332be, there are 
warnings in blead when a malformed UTF-8 character is tested for being 
an alpha, punct etc.

The warning message is like:
It is deprecated to pass malformed UTF-8 to character classification 
macros, for "_Perl_IDStart" at op/ref.t line 506.

(I'm open to better wording suggestions)

There are several test files that now generate these messages.  I 
suspect that they are the result of bugs being unmasked by this new 
warning.  I will not be able to look at them until after the visible 
code changes freeze in late February.

Below is a list of the test files in case someone who has particular 
expertise in any of them wishes to investigate sooner than I can.

t/op/ref.t
t/uni/package.t
ext/XS-APItest/t/svpv_magic.t

• New warnings in blead (was RFC: deprecate calling isFOO_utf8() withmalformed UTF-8) by Karl Williamson
• Re: New warnings in blead (was RFC: deprecate calling isFOO_utf8()with malformed UTF-8) by Aristotle Pagaltzis
• Re: New warnings in blead (was RFC: deprecate calling isFOO_utf8()with malformed UTF-8) by Karl Williamson
• Re: New warnings in blead (was RFC: deprecate calling isFOO_utf8()with malformed UTF-8) by Dave Mitchell
• Re: New warnings in blead (was RFC: deprecate calling isFOO_utf8()with malformed UTF-8) by Karl Williamson
• Re: New warnings in blead (was RFC: deprecate calling isFOO_utf8()with malformed UTF-8) by Nicholas Clark