Initial work on Windows build script
windows: Build fixes on Cygwin

gtk-update-icon-cache is needed to build Gtk.

celt needs libogg headers and Autoconf macros, but doesn't need libogg
at runtime, so we use the system copy.
windows: Only support building from Cygwin
windows: Have setup command install Python and pure Python modules
windows: Fix celt build

Disable ogg support during celt build.  We still need libogg-devel for
the Autoconf macro.
windows: Handle artifacts outside bin directory in generic code
windows: Add pycairo
windows: Fix gst-plugins-base build
windows: Add pygobject
windows: Remember to pass -f to autoreconf
windows: Minor cleanup
windows: Add PyGTK
windows: Update spice-gtk to 0.21
windows: Build spice-gtk Python module