libx11-xcb-dev 2:1.4.2-1ubuntu2 (amd64 binary) in ubuntu natty

 libX11-xcb provides functions needed by clients which take advantage of
 Xlib/XCB to mix calls to both Xlib and XCB over the same X connection.
 .
 This package contains the development headers for the library found in
 libx11-xcb1. Non-developers likely have little use for this package.
 .
 More information about X.Org can be found at:
 <URL:http://www.X.org>
 .
 More information about XCB can be found at:
 <URL:http://xcb.freedesktop.org>
 .
 This module can be found at
 git://anongit.freedesktop.org/git/xorg/lib/libX11