drisw: Fix 24bpp software rendering, take 2

This patch add the support for 24bpp in the dri/swrast implementation.
See http://bugs.freedesktop.org/show_bug.cgi?id=23525

Signed-off-by: Marc Pignat <marc at pignat.org>
Signed-off-by: Brian Paul <brianp@vmware.com>

src/glx/drisw_glx.c

@@ -100,6 +100,13 @@ XCreateDrawable(struct drisw_drawable * pdp,
                               32,                     /* bitmap_pad */
                               0);                     /* bytes_per_line */
 
+  /**
+   * swrast does not handle 24-bit depth with 24 bpp, so let X do the
+   * the conversion for us.
+   */
+  if (pdp->ximage->bits_per_pixel == 24)
+     pdp->ximage->bits_per_pixel = 32;
+
    return True;
 }