Don't insert padding between lists in requests

Lists of types that have the same padding as each other should not have any padding automatically inserted by libxcb.

Fixes xcb_randr_set_crtc_gamma when "size" is an odd number.

Incidentally fixes incorrect padding when the request is built out-of-line (as when c_need_serialize is set), not that there are any such requests in the xorg tree that end without padding.

Depends on xorg/proto/xcbproto!14 (merged) in order to avoid breaking xcb_glx_set_client_info_arb and xcb_glx_set_client_info_2arb (and also a couple of xprint requests, not that anybody uses xprint).