Correct prototype on set_completion.
In support of out-of-process command completion. The debugger "complete" command however is needs work.
Client.pm: correct command completion by giving entire line.
Util.pm: Work around Perl feature where 0 like '' is interpreterd as false.
*: start to use utf8 more.
Client.pm: correct command completion by giving entire line. Util.pm: Work around Perl feature where 0 like  is interpreterd as false. *: start to use utf8 more.