The canonical way to detect EOF on read is when you request more than
zero bytes, but zero bytes come back.  Switching to this method seems
to handle a few problem cases better.  Also handle ERROR_BROKEN_PIPE
properly just in case.

wined3d: Add read_from_framebuffer_texture which combines code from read_from_framebuffer (drawpixels) and LoadLocation.

This makes the code easier to read and the pieces borrowed from
read_from_framebuffer are more correct than the code in LoadLocation.