[Xcb] compiler padding and sync extension

[Aaron Young]

While playing around with the sync extension using XCB, I've
apparently come across the same issue mentioned here:
http://lists.freedesktop.org/archives/xcb/2007-August/002970.html,
which seems to have fallen between the cracks somewhere.

I'm no expert, but I was a little surprised to discover that XCB
structures weren't already defined with __attribute__ ((packed)),
#pragma pack(1), etc.  Any reason this approach hasn't been adopted?
Does the sync extension not get enough use to warrant fixing this?

Regards,
Aaron