Make print, syswrite, send, readline, getc honour utf8-ness of PerlIO.

(sysread, recv and write i.e. formats still to do...)
Allow :utf8 or :bytes in PerlIO_apply_layers() so that
   open($fh,">:utf8","name")
etc. work. - "applying" those just sets/clears the UTF8 bit of the top layer,
so no extra overhead is involved.
Tweak t/comp/require.t to add a 'use bytes' to permit its dubious writing of BOM
to a non-utf8 stream.
Add initial io/utf8.t
Fix SvPVutf8() - sv_2pv() was not expecting to be called with something
that was already SvPOK() - (we just fossiked with SvUTF8 bit). Fix that
and also just use the SvPV macro in sv_2pvutf8() to avoid the issue/overhead.

p4raw-id: //depot/perlio@8054

1 files changed, 8 insertions, 6 deletions

diff --git a/doio.c b/doio.c
index 901ca718d0..d8168e1636 100644
--- a/doio.c
+++ b/doio.c
@@ -1148,12 +1148,14 @@ Perl_do_print(pTHX_ register SV *sv, PerlIO *fp)
 	}
 	/* FALL THROUGH */
     default:
-#if 0
-	/* XXX Fix this when the I/O disciplines arrive. XXX */
-	if (DO_UTF8(sv))
-	    sv_utf8_downgrade(sv, FALSE);
-#endif
-	tmps = SvPV(sv, len);
+	if (PerlIO_isutf8(fp)) {
+	    tmps = SvPVutf8(sv, len);
+	}
+	else {
+	    if (DO_UTF8(sv))
+		sv_utf8_downgrade(sv, FALSE);
+	    tmps = SvPV(sv, len);
+	}
 	break;
     }
     /* To detect whether the process is about to overstep its