ParseXS: refactor: add Node::OUTPUT_line fields

This is #6 of a small series of commits to refactor OUTPUT keyword
handling.

The main job of parsing an OUTPUT line is to extract any information on
that line and use it to update the associated Param object (which was
likely created earlier when the XSUB's signature was parsed).

This commit makes that information also be stored in new fields in the
OUTPUT_line object. These new fields aren't currently used for anything,
but they could in principle become useful if options for deparsing or
exporting were added to ParseXS.

Author: iabyn

dist/ExtUtils-ParseXS/lib/ExtUtils/ParseXS/Node.pm

@@ -3053,7 +3053,11 @@ package ExtUtils::ParseXS::Node::OUTPUT_line;
 # Handle one line from an OUTPUT keyword block
 
 BEGIN { $build_subclass->('keyline', # parent
-    'param', # the param object associated with this OUTPUT line.
+    'param',       # the param object associated with this OUTPUT line.
+    'is_setmagic', # bool: the line is a SETMAGIC: line
+    'do_setmagic', # bool: the current SETMAGIC state
+    'name',        # name of the parameter to output
+    'code',        # optional setting code
 )};
 
 
@@ -3069,8 +3073,16 @@ sub parse {
 
     return unless $line =~ /\S/;  # skip blank lines
 
+    # set some sane default values in case we do one of the early returns
+    # below
+
+    $self->{do_setmagic} = $pxs->{xsub_SETMAGIC_state};
+    $self->{is_setmagic} = 0;
+
     if ($line =~ /^\s*SETMAGIC\s*:\s*(ENABLE|DISABLE)\s*/) {
         $pxs->{xsub_SETMAGIC_state} = ($1 eq "ENABLE" ? 1 : 0);
+        $self->{do_setmagic} = $pxs->{xsub_SETMAGIC_state};
+        $self->{is_setmagic} = 1;
         return;
     }
 
@@ -3080,6 +3092,8 @@ sub parse {
     #
     my ($outarg, $outcode) = $line =~ /^\s*(\S+)\s*(.*?)\s*$/s;
 
+    $self->{name} = $outarg;
+
     my ExtUtils::ParseXS::Node::Param $param =
                                         $pxs->{xsub_sig}{names}{$outarg};
     $self->{param} = $param;
@@ -3106,7 +3120,7 @@ sub parse {
     $param->{do_setmagic} = $outarg eq 'RETVAL'
                                 ? 0 # RETVAL never needs magic setting
                                 : $pxs->{xsub_SETMAGIC_state};
-    $param->{output_code} = $outcode if length $outcode;
+    $self->{code} = $param->{output_code} = $outcode if length $outcode;
 
     if ($outarg eq 'RETVAL') {
         # Postpone processing the RETVAL line to last (it's left to the