Delete a useless level of indirection from _xcb_out_send's parameters.

Delete a useless level of indirection from _xcb_out_send's parameters.

_xcb_out_send needs _xcb_conn_wait to store back its progress so it can
be reinvoked to pick up where it left off---but then _xcb_out_send
guarantees that it leaves either an empty output vector or a shut-down
connection, so *its* callers never care how much progress was made.

Signed-off-by: Jamey Sharp <jamey@minilop.net>
Reviewed-by: Josh Triplett <josh@freedesktop.org>