giscanner: remove Python xml attribute formatter

There's no sense in keeping it around as it is never
used. And even though measuring the time it takes to
build Gtk-3.0.gir using a) the C version and b) the
Python version reveals there is no measurable difference
to speak of (when *not* running under Python's cProfile
module):

With C collect_attributes:
==========================

real	0m30.614s
real	0m32.255s
real	0m31.034s

With Python collect_attributes:
===============================

real	0m31.530s
real	0m31.549s
real	0m31.673s

The C version ends up using g_markup_escape_text() which
will escape \004 as &#x4;. Even though this is invalid
xml 1.0 (but valid xml 1.1), the Python version leaves
the \004 as is, which is even less desirable...
[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

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