Declare `=encoding` ASAP

In some cases the file is not slurped so declaring encoding at the tail
is useless.

src/include-bash/sfdoc.sh

     echo "true <<'=cut'"
     echo "=pod"
     echo
+    echo "=encoding $Encoding"
+    echo
     echo "=head1 NAME"
     echo
     echo "$MName - $(__sfdoc__get_doc | head -1)"
         echo "=back"
         echo
     }
-    echo "=encoding $Encoding"
     echo "=cut"
 }