[gtk-doc] scan: comment the handling for opaque structs a bit more

[Stefan Sauer <stefkost src gnome org>]

commit da0ba95f6d4a0b46cb170aa553ff9c8bb9fdf046
Author: Stefan Sauer <ensonic users sf net>
Date:   Fri Feb 1 07:34:41 2019 +0100

    scan: comment the handling for opaque structs a bit more

 gtkdoc/scan.py | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)
---
diff --git a/gtkdoc/scan.py b/gtkdoc/scan.py
index 96a33f5..edc0bbd 100644
--- a/gtkdoc/scan.py
+++ b/gtkdoc/scan.py
@@ -665,7 +665,8 @@ def ScanHeaderContent(input_lines, decl_list, get_types, options):
                 # We've found a 'typedef struct _<name> <name>;'
                 # This could be an opaque data structure, so we output an
                 # empty declaration. If the structure is actually found that
-                # will override this.
+                # will override this (technically if will just be another entry
+                # in the output file and will be joined when reading the file).
                 structsym = cm[8].group(1).upper()
                 logging.info('%s typedef: "%s"', structsym, cm[8].group(2))
                 forward_decls[cm[8].group(2)] = '<%s>\n<NAME>%s</NAME>\n%s</%s>\n' % (