Integrate:

Integrate:
[ 18715]
The new(er) way of controlling Unicode I/O (and other) features;
-C (or PERL_UNICODE).  See perlrun/-C for more details.

[ 18716]
Forgotten from #18715.

[ 18717]
Clarify the -C syntax a bit.

[ 18730]
Make also the -CAL conditional on locale.

[ 18731]
Doc tweaks (and one code tweak) based on Philip Newton's comments.

[ 18732]
Philip Newton has eagle eyes :-)

[ 18741]
Format nit.
p4raw-link: @18741 on //depot/perl: d5fb0cc6f61f4be5573cf82c6eec2f249c3cf390
p4raw-link: @18732 on //depot/perl: f3f8427d8eb74488a7768102783b300690126cdc
p4raw-link: @18731 on //depot/perl: 8aa8f774be44d46814d4ddbad03e302f1eb37338
p4raw-link: @18730 on //depot/perl: ce81ff128f8fe94cb13ace56aa6d974168cbdf12
p4raw-link: @18717 on //depot/perl: 9f21530fbfcfd9e38d6db2986fb0ca799bda8f60
p4raw-link: @18716 on //depot/perl: eb7b3f484a407c1bbfe89627adaeb5edc5e77736
p4raw-link: @18715 on //depot/perl: a05d7ebb5e798334196e3cff205b658506cc4384

p4raw-id: //depot/maint-5.8/perl@18742
p4raw-integrated: from //depot/perl@18716 'merge in' embed.h (@18660..)
	proto.h (@18668..)
p4raw-integrated: from //depot/perl@18715 'merge in' embedvar.h
	intrpvar.h perlapi.h (@18490..) perl.h (@18530..) embed.fnc
	(@18660..)
p4raw-integrated: from //depot/perl@18701 'copy in' locale.c
	pod/perlunicode.pod pod/perluniintro.pod (@18715..)
	pod/perlrun.pod (@18731..) 'edit in' pod/perlvar.pod (@18715..)
	perl.c (@18727..) util.c (@18731..) 'merge in' pod/perldiag.pod
	(@18280..) gv.c (@18490..) mg.c (@18633..)