Set visual depth to 24 for 32 bits-per-pixel devices on Win32. This allows

2005-10-13  Tor Lillqvist  <tml@novell.com>

	Set visual depth to 24 for 32 bits-per-pixel devices on
	Win32. This allows gdk_drawable_real_draw_pixbuf() to use the
	optimized composite_0888() function rather than the slower image
	dithering functions to draw pixbufs (#313993, John Ehresman)

	* gdk/win32/gdkimage-win32.c (_gdk_win32_new_image): Use
	_gdk_windowing_get_bits_for_depth() to initialize
	GdkImage::bits_per_pixel.
	(_gdk_windowing_get_bits_for_depth): Return 32 bits for depth 24.

	* gdk/win32/gdkpixmap-win32.c (gdk_pixmap_new): Use
	_gdk_windowing_get_bits_for_depth() to initialize
	BITMAPINFOHEADER::biBitCount.

	* gdk/win32/gdkvisual-win32.c (_gdk_visual_init): Set
	GdkVisual::depth to 24 even if GetDeviceCaps(BITSPIXEL) returns
	32.