giscanner: write '<varargs/>' instead of '<varargs></varargs>'
giscanner: don't accept (allow-none) on Returns:

The old annotationparser.py happily parsed this, but
giscanner/girwriter.py never serialized an allow-none
attribute to the .gir file and girepository/girparser.c
never looked for an allow-none attribute either.
giscanner: remove unneeded isinstance check

_write_class() is only ever called with ast.Class
and ast.Interface nodes so the check served no purpose
other than contribute to global warming...
[WIP] Add a tool fixing GTK-Doc comment blocks in .c and .h files

Just a standalone script for now, should probably eventually
go into g-ir-doctool or g-ir-annotation-tool...
[WIP] giscanner: include linemarkers in "gir/[gio|glib|gobject]-2.0.c"

Makes it obvious where a GTK-Doc comment block was picked up.

Note that these are not C pre-processor style linemarkers on
purpose to prevent g-ir-scanner's SourceScanner() from tripping
up over the non-absolute paths in the generated
"gir/[gio|glib|gobject]-2.0.c" files.
[wip]: gir xml schema

find ~/gnome.org/prefix/share/gir-1.0/ -name "*.gir" -exec xmllint --noout --nonet --schema ~/gnome.org/checkout/gobject-introspection/giscanner/gir/gir-1.2.xsd '{}' \;
[WIP] docs: improve layout
!!! for testing only !!!