Remove superfluous &utf8::AUTOLOAD

Historically this was used to load utf8_heavy.pl before calling the real
functions but now that utf8_heavy.pl is no longer a thing it doesn't
serve any purpose. The error message upon calling an unknown sub changes
by one character since it now comes from perl proper rather than a
hand-rolled one in utf8.pm.

I've added a comment, modeled on the one in builtin.pm, to explain
where the subs are actually defined.

Author: JRaspass

lib/utf8.pm

@@ -1,13 +1,16 @@
 package utf8;
 
+# This file only defines the import/unimport subs, the rest are implemented by
+# always-present functions in the perl interpreter itself.
+# See also `universal.c` in the perl source
+
 use strict;
 use warnings;
 
 our $utf8_hint_bits  = 0x00800000;
 our $ascii_hint_bits = 0x00000010;  # Turned off when utf8 turned on
 
-our $VERSION = '1.27';
-our $AUTOLOAD;
+our $VERSION = '1.28';
 
 sub import {
     $^H |= $utf8_hint_bits;
@@ -18,12 +21,6 @@ sub unimport {
     $^H &= ~$utf8_hint_bits;
 }
 
-sub AUTOLOAD {
-    goto &$AUTOLOAD if defined &$AUTOLOAD;
-    require Carp;
-    Carp::croak("Undefined subroutine $AUTOLOAD called");
-}
-
 1;
 __END__
 

lib/utf8.t

@@ -557,8 +557,8 @@ SKIP: {
 
 {
     fresh_perl_like ('use utf8; utf8::moo()',
-		     qr/Undefined subroutine utf8::moo/, {stderr=>1},
-		    "Check Carp is loaded for AUTOLOADing errors")
+		     qr/Undefined subroutine &utf8::moo/, {stderr=>1},
+		    "Check undefined subroutines error")
 }
 
 {