* glom/libglom/sharedptr.h: Added operator!=.

	* glom/mode_data/flowtablewithfields.h:
	* glom/mode_data/flowtablewithfields.cc: Added set_other_field_value
	which is the same as set_field_value except that it does not set the
	value for widget that belongs to the passed layout item's widget
	itself. This can be used if that very widget already contains the new
	value to avoid setting it again. Especially when dealing with large
	images this brings an essential speedup.

	* glom/mode_data/box_data_details.cc (on_flowtable_field_edited): Use
	set_other_field_value, so that we don't set the value for the field
	which the user already changed again.

	* glom/utility_widgets/imageglom.h:
	* glom/utility_widgets/imageglom.cc: Store the original data of the
	image file, and return it in get_value(), instead of creating a PNG
	from the raw image data, to speed up loading a large image file.

	* glom/utils_ui.cc (get_pixbuf_for_gda_value): When loading images
	from the database, allow all image types, not just PNGs.

	* glom/xsl_utils.cc: Include gtk/gtk.h to fix the build for me.