pidgin/pidgin

Change the last param of yahoo_string_encode from gboolean* to gboolean.

There was no reason for it to be a pointer. Maybe someone wanted to
optionally set utf-8 to true if we needed it or something? But that's
not the current behavior. It's better for the code to be simpler now,
and it can be changed back to a pointer if we need it for some reason.
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