window: Make icon setting 64-bit safe
window: Make icon setting 64-bit safe

Use gulong instead of int, which will do the right thing on 64-bit. Also
check the return result of the second cogl_texture_get_data call to make
sure it's returning what it promised in the first.

pwithnall/mx,jonnylamb/mx,clutter-project/mx,jonnylamb/mx,jonnylamb/mx,pwithnall/mx,clutter-project/mx,pwithnall/mx,pwithnall/mx,clutter-project/mx,clutter-project/mx,jonnylamb/mx