Update to 2.20.1.

Parts were split off into a separate package which I'll commit shortly,
gnome-desktop-sharp.

Changes:
* bootstrap-2.20: bump version.
* bootstrap-generic: substitute the GTK_SHARP_REQUIRED_VERSION.
* bootstrap-2.20: check for gtk 2.12.0 and gtk-sharp 2.12.1.
* configure.in.in: separate the gtk+ and gtk-sharp version variables.
* gnome/Program.custom: use GLib.Object.Harden to avoid some
reflection.
* bootstrap-2.20: bump gtk-sharp requirement to 2.12.1.
* gnome/Program.custom: revert QuitPrepare hook and instead do an
obnoxious hack to disable the toggle_ref mechanism for GnomeProgram.
Uses reflection since I didn't want to expose this hack in the public
GLib.Object API.
* gnome/Program.custom: hook into Gtk.Application.QuitPrepare to
dispose our managed resources prior to invoking gtk_main_quit.  Avoids
a crash on exit() in toggle_ref usage after managed releases have been
released.
* bootstrap-2.20: bump version and tag.
* gnome/gnome-api-2.20.raw: reparse
* sources/gnome-sharp-2.20-sources.xml: hide private gailcanvas hdrs.
hide gnome-print-gdi.h.
* bootstrap-2.20: bump svn version.
* gnome/Gnome.metadata: hide new Global class which was hiding
stable API.  [Fixes #356649]
* configure.in.in: integrate build service patch from Wade.
* bootstrap-2.20: update to version 2.19.90.
* * Move to 2.20 API.
* configure.in.in: move vte, rsvg, and gtkhtml to gnome-desktop-sharp.
* Makefile.am: ditto
* sample/Makefile.am: ditto
* Makefile.include: some refinement of the variable mangling.
* configure.in.in: expand new pc.in.
* gconf/GConf/gconf-sharp-2.0.pc.in: remove gnome-sharp Requires and
peditors.dll from the Libs: var.
* gconf/GConf.PropertyEditors/Makefile.am: install new pc.
* gconf/GConf.PropertyEditors/gconf-sharp-peditors-2.0.pc.in: expose
new pc file since this is conditional and the gconf-sharp.dll build
is not.
* gconf/GConf/Makefile.am: Copy AssemblyInfo.cs to the current dir so
that csc can find it.  (csc doesn't understand ../..)
* gconf/GConf/Makefile.am:
* gconf/GConf.PropertyEditors/Makefile.am:
use top_builddir instead of .. to avoid win32 build issues.
* gconf/GConf/Makefile.am: remove GNOME condition.  It's only needed
on the peditor build.
* gnome/CanvasItem.custom: marshal GType as IntPtr.
[Fixes comment #8 of 327058]
* gconf/GConf/Value.cs: Deal with zero length arrays gracefully.
Thanks to Sebastian Dr旦ge <slomo@circular-chaos.org> for a
patch this one was derived from.  [Fixes #325516]
* AssembyInfo.cs.in : add [IgnoreClassInitializers]
* vte/Vte.metadata : rule from Peter Johanson to mark a string
const.
* gnome/CanvasPathDef.custom : adapt to generated pinvoke sig change.
* configure.in.in : add blurb about the gnome-sharp.dll requirements
since it seems to be a FAQ for people trying to build from sources.
* bootstrap-generic : use automake --foreign to keep automake-1.10 from
blowing up on the gnu make function usage.  grrr.
* sample/gconf/Makefile.am : use install-data-hook to make 1.10 happy.
* gconf/tools/gconfsharp2-schemagen.in:
Revert unportable 'relocatable' wrapper using which (doesn't work with symlinks)
* gconf/GConf/Value.cs: Allow the storage of empty lists in
gconf-sharp.

(wiz)