Clarification: use encoding cannot be used to

Clarification: use encoding cannot be used to
change the default encoding of "your whole script";
only the default encoding of the *data*.  Also, it
seems that "use encoding" does not mix with "use utf8"
(a coredumping recursion ensues).  Should not be a huge
problem since "use utf8" is pretty marginal nowadays.

p4raw-id: //depot/perl@12786