All remaining cases of "use utf8" lie in the testsuite.  As "use utf8"
changes the semantics of dealing with Unicode strings, remove it to
allow programmers to always assume that literals are interpreted as
bytestrings, not characters.  To do otherwise means that one must always
ask if "use utf8" is in scope before performing operations on any
literals; instead, simply make the encodings and decodings explicit.

Note that wide characters may appear in editors, and that the encoding
of the characters on _disk_ will always be UTF-8.  The removal of "use
utf8" merely means that perl will generate a two-byte string from "é",
and not a one-character string.