[Xcb] 0 sequence number for request errors?

[Vincent Torri]

> I did change the extension API in this patch. That API is public but at
> present the only code that uses it is inside XCB itself and that's
> autogenerated, so I'm not too concerned about it. Also the change makes
> xproto.o another kilobyte smaller (that's 7%!) on x86 with gcc 3.4.5
> -O3 -- and I assume the extensions got smaller too. So there. ;-)

maybe we should try the hidden-visibility feature of gcc 4.*. I've
experienced a big decrease of the size of the libraries with other
projects.

Also, stripping the library can decrease its size too. I don't think that
we use it.

Vincent